bluuebunny/crossref_metadata_2025 huggingface dataset:
SECRETION RATE AND METABOLIC CLEARANCE RATE OF PROLACTIN IN THE RAT DURING MID- AND LATE LACTATION
Authors: GROSVENOR C. E. , WHITWORTH N. S.
Published: December 2008

The prolactin concentration in the plasma of lactating rats rose less rapidly and attained a significantly lower plateau level in response to suckling on day 20–21 of lactation than it did on day 13–14 of lactation. Neither differences in suckling stimulation of the older pups nor a higher metabolic clearance rate (MCR) of prolactin were implicated in the reduced prolactin concentration seen in the late-lactating rats. The MCR was, in fact, slightly reduced in both conscious and late-lactating rats anaesthetized with urethane when compared with those in mid-lactation. The MCR of prolactin was not significantly altered by urethane anaesthesia in rats on either day of lactation. However, the secretion rate of prolactin, computed from the MCR multiplied by the equilibrum concentration of prolactin during suckling, was considerably reduced (665 to 392 ng/min) from mid- to late lactation. We conclude from these data that the reduced plasma concentration of prolactin in response to suckling in late lactation is the result of an impairment within the prolactin secretory mechanism.
SERUM PROLACTIN LEVELS IN CASTRATED RAMS AT VARIOUS TIMES OF THE YEAR AND DURING TREATMENT WITH ANDROGENS OR OESTROGEN
Authors: PARROTT R. F. , HILLS F.
Published: December 2008

Prolactin concentrations were measured in serum from wethers at various times of the year before and during treatment with testosterone propionate, dihydrotestosterone propionate, 19-hydroxytestosterone dipropionate and oestradiol dipropionate. Levels of prolactin in serum were lower in untreated wethers during short (October) than during long (April–August) days. Seasonal differences persisted throughout the experiment but became less obvious during treatment with oestradiol dipropionate and 19-hydroxytestosterone dipropionate, both of which raised prolactin concentrations. Neither testosterone propionate nor dihydrotestosterone propionate altered the levels of prolactin.
CONCENTRATION OF 5-METHOXYTRYPTOPHOL IN PINEAL GLAND AND PLASMA OF THE RAT
Authors: CARTER S. J. , LAUD C. A. , SMITH I. , LEONE R. M. , HOOPER R. J. L. , SILMAN R. E. , FINNIE M. D. A. , MULLEN P. E. , LARSON-CARTER D. L.
Published: December 2008

5-Methoxytryptophol, a serotonin metabolite, was measured by gas chromatography–mass spectrometry in pineal glands, plasma and control tissues (cerebral cortex and salivary glands) from male rats kept in a controlled lighting environment. In the pineal gland the level of 5-methoxytryptophol was significantly higher during the dark period than during the light, the absolute levels being an order of magnitude less than those of melatonin. In the plasma, the levels showed a reverse situation with respect to lighting conditions. No correlation was found between the 5-methoxytryptophol levels in plasma and the pineal gland in individual animals. These results suggest that there is no obvious correlation between pineal content and pineal activity. This may be due to a combination of rapid turnover, secretion and/or peripheral conversion of another 5-methoxyindole to 5-methoxytryptophol.
PROGESTERONE RECEPTORS AND RNA POLYMERASE ACTIVITY IN THE RAT UTERUS DURING THE OESTROUS CYCLE
Authors: KURL R. N. , BORTHWICK N. M.
Published: December 2008

The concentrations of progesterone receptors in uterine cytoplasm and nuclei were measured during the oestrous cycle of the rat. The concentration of cytoplasmic progesterone receptors was highest at pro-oestrus and declined at oestrus to reach lowest levels at metoestrus before rising at dioestrus. Similar changes were observed in the concentration of nuclear progesterone receptors, the highest levels being present at pro-oestrus and dioestrus. In addition, both activities A and B of RNA polymerase mirrored these alterations in nuclear receptor levels.
HORMONE REPLACEMENT THERAPY IN THE MENOPAUSE: A SUITABLE ANIMAL MODEL
Authors: PAPADAKI LUCIENNE , BEILBY J. O. W. , CHOWANIEC JANINA , COULSON W. F. , DARBY A. J. , NEWMAN J. , O'SHEA A. , WYKES J. R.
Published: December 2008

Female CBA mice, aged 11 months, were treated cyclically with oral ethynyl oestradiol or oestrone sulphate for 3 months. The ovaries of all animals appeared to be atrophied. Target tissues throughout the genital tract showed a response to both oestrogens. Electron microscopy of both the endometrium and the urothelium demonstrated morphological changes characteristic of increased cellular metabolic activity in the treated mice. Endometrial hyperplasia developed in both treatment groups but more pronounced epithelial changes occurred with oestrone sulphate. This hyperplasia was accompanied by a doubling in the number of uterine cytoplasmic oestrogen receptors. A 50% fall in serum levels of luteinizing hormone in the treated mice revealed that the hypothalamic-pituitary system was still intact. Both oestrogens improved skeletal balance by changes in cortical-endosteal bone remodelling. The results suggest that the CBA strain of mouse is a suitable model for the study of the human climacteric and its response to hormone replacement therapy.
STIMULATION OF CARTILAGE ZONES OF THE CALF COSTOCHONDRAL GROWTH PLATE IN VITRO BY GROWTH HORMONE DEPENDENT RAT PLASMA SOMATOMEDIN ACTIVITY
Authors: HILL D. J.
Published: December 2008

The actions of rat plasma somatomedin activity dependent on growth hormone were investigated in vitro on separated zones of cartilage from the calf costochondral junction. Plasma somatomedin maximally stimulated the uptake of [3H]thymidine into cartilage cells of the proliferating region. Cartilage deeper in the growth plate possessed the highest uptake of [35S]sulphate which was also stimulated by somatomedin. Somatomedin, therefore, appears to promote both cell replication and matrix synthesis throughout the growth plate cartilage although the two processes were greatest in different cartilage regions. Growth hormone or tri-iodothyronine did not directly alter the uptake of either isotope into the growth plate cartilage.
ACUTE EFFECTS OF ALDOSTERONE ON WATER AND ELECTROLYTE TRANSPORT IN THE COLON AND COPRODEUM OF THE DOMESTIC FOWL (GALLUS DOMESTICUS) IN VIVO
Authors: THOMAS D. H. , SKADHAUGE ERIK , READ M. W.
Published: December 2008

White Leghorn laying hens were maintained on commercial poultry food (medium-Na+ diet) and fresh water. High-Na+ diet birds received, in addition, 10 ml 9% (w/v) NaCl/kg by stomach load for 2 days before perfusion experiments. The lumen of the coprodeum and colon of anaesthetized birds was perfused with a hyperosmotic solution resembling ureteral urine. Transmural solute and water fluxes and potential difference (p.d.) values were measured for 2·5 h before and for 8 h after i.v. injection of aldosterone (120 μg/kg). After administration of aldosterone, the lag, increasing and stabilized plateau phases were identified for Na+, K+ and Cl− fluxes (which together formed an electroneutral ion-exchange system); plateau flux values were significantly greater than preinjection values and were comparable to values for birds maintained on low-Na+ diets in parallel experiments. Ammonium, phosphate and water fluxes were unresponsive to aldosterone and p.d. values showed a transient increase in medium-Na+ diet birds only. In parallel experiments on birds on low sodium diets the ammonium flux and p.d. increased but the osmotic flow and phosphate transfer did not respond. Therefore acute injection of aldosterone reproduced some but not all of the responses to dietary Na+ restriction in fowls.
USE OF A PULSED INFUSION OF LUTEINIZING HORMONE RELEASING HORMONE TO MIMIC SEASONALLY INDUCED ENDOCRINE CHANGES IN THE RAM
Authors: LINCOLN G. A.
Published: December 2008

Adult Soay rams were housed indoors under natural lighting during the spring non-mating season when gonadotrophin secretion was low. Four animals received small doses (100 ng or 500 ng) of synthetic LH releasing hormone (LH-RH) infused into the jugular vein by a mechanical device for 60 s every 2 h for 33–57 days: two other rams acted as controls. The prolonged treatment with LH-RH resulted in growth of the testes and the development of the sexual skin flush; these effects were lost when treatment stopped. The plasma concentrations of LH, FSH and testosterone were low at the beginning; each short infusion of LH-RH resulted in a transitory increase in the level of LH and testosterone while the concentration of FSH was only marginally affected. After prolonged treatment with 500 ng pulses of LH-RH the plasma concentrations of all three hormones were permanently raised. The response to the individual injections of LH-RH was also modified, the peak in LH being reduced in amplitude but more prolonged while the FSH and testosterone responses were both enhanced. When the pulsed infusion was stopped the concentration of LH and testosterone declined rapidly while the decline in FSH levels took many days. These endocrine changes induced by the pulsed infusion are comparable to those that occur naturally in the ram during testicular redevelopment before the mating season.
INTERACTION BETWEEN THEOPHYLLINE AND OESTROGEN IN THE RAT UTERUS
Authors: STEINSAPIR J. , ROJAS A. M. , FERNÁNDEZ A. , ALBURQUERQUE M. , LEÓN S. , BUSTÓN P. , PACHECO R. , MUNIZAGA A. , HABASH L. , OJEDA J. M. , TCHERNITCHIN A.
Published: December 2008

Theophylline alone or in the presence of 0·001, 0·01, 0·1 or 1 μg oestradiol-17β/100 g body wt increased uterine RNA and protein content 6 h after administration. Uterine oedema induced by physiological doses of oestradiol-17β was increased further in the presence of theophylline.

Theophylline decreased the number of eosinophils in the blood and concurrently decreased oestrogen-induced uterine eosinophilia at doses of 0·01,0·1, 1,10 or 30 μg oestradiol-17β/100 g body wt. Oestrogen binding by uterine eosinophils in vitro increased in the presence of theophylline. This effect of theophylline could explain the increase of oestrogen-induced uterine oedema in vivo.
CIRCANNUAL CHANGES IN PLASMA CONCENTRATIONS OF IMMUNOREACTIVE RETINOL-BINDING PROTEIN AND LUTEINIZING HORMONE IN MALE AND FEMALE JAPANESE QUAIL
Authors: HEAF D. J. , GLOVER J.
Published: December 2008

In a single experiment, lasting for 18 months, male and female quail were exposed to an annual cycle of artificial photoperiod synchronized with sunrise and sunset, and their plasma levels of immunoreactive retinol-binding protein (IRBP) and LH were monitored at frequent intervals. Plasma levels of both IRBP and LH showed a repeating annual cycle with maximal levels during the spring/summer, the period of reproductive activity and highest rate of egg-laying, and minimal levels during the autumn/winter. Plasma levels of IRBP and LH were significantly, but only weakly, correlated with each other. The possible role of LH in the regulation of plasma IRBP during reproduction is discussed. Evidence is presented that the proportion of IRBP which does not carry retinol (retinol-binding apoprotein; apoRBP) varies throughout the female breeding cycle and that the high apoRBP concentration noted in the spring/summer period may be related to the deposition of retinol in the egg.
NON-PROTEIN-BOUND OESTROGENS IN PLASMA AND URINARY EXCRETION OF UNCONJUGATED OESTROGENS IN NON-PREGNANT WOMEN
Authors: SPEIGHT ALISON C. , HANCOCK K. W. , OAKEY R. E.
Published: December 2008

The concentrations of oestrone and oestradiol-17β in peripheral plasma and the urinary excretion of unconjugated oestrone and unconjugated oestradiol-17β were measured by radioimmunoassay in 31 matched samples from seven young women. The concentrations of oestrone and oestradiol-17β not bound to protein in the plasma samples were measured following equilibrium dialysis.

The urinary excretion of unconjugated oestrone (0·70 ± 0·34 nmol/24 h, mean ±s.d., n = 28) was found to be significantly, but poorly, correlated with the concentration of non-protein-bound oestrone in plasma (10·2 ± 3·8 pmol/l) (r = 0·44, P < 0·05). Similarly, the urinary excretion of unconjugated oestradiol-17β (0·29 ± 0·16 nmol/24 h, n = 30) was found to be significantly, but still rather poorly correlated with the concentration of non-protein-bound oestradiol-17β in plasma (7·4 ± 5·3 pmol/l) (r = 0·58, P< 0·001). Since the calculated proportions of oestrone and oestradiol-17β in plasma not bound to protein (3·4 ± 0·3% and 1·7 ± 0·2% respectively) remained fairly constant (coefficient of variation 9 and 10% respectively), measurement of oestrone or oestradiol-17β in plasma provided a better guide to the biologically available (non-protein-bound) hormone than did measurement of urinary unconjugated oestrogen.

The mean renal clearance of both non-protein-bound oestrone and non-protein-bound oestradiol-17β (50 ± 21 and 36 ± 23 ml/min) was less than that of creatinine (114 ± 31 ml/min) indicating absorption and/or metabolism of each hormone by the kidney tubule.
PROPERTIES OF RAT ADRENAL ZONA RETICULARIS CELLS: PRODUCTION AND STIMULATION OF CERTAIN STEROIDS
Authors: BELL J. B. G. , GOULD R. P. , HYATT P. J. , TAIT J. F. , TAIT S. A. S.
Published: December 2008

The outputs of corticosterone, deoxycorticosterone and androstenedione from dispersed, purified rat adrenal zona reticularis and zona fasciculata cells have been measured by radioimmunoassay.

Preferential production of deoxycorticosterone by zona reticularis cells was demonstrated by their higher basal deoxycorticosterone: corticosterone ratio when compared with zona fasciculata cells.

Adrenocorticotrophin (ACTH) stimulated corticosterone output by all cell pools prepared by unit gravity (1 g) sedimentation, zona fasciculata cells being stimulated 130-fold compared with 20-fold for the zona reticularis cells in relation to their basal corticosterone output.

In every cell pool, ACTH stimulated the output of corticosterone more than it stimulated the output of deoxycorticosterone. In parallel cell preparations, it was shown that ACTH increased the conversion of tracer amounts of radioactive deoxycorticosterone to corticosterone and decreased the conversion of radioactive corticosterone to 11-dehydrocorticosterone. Adrenocorticotrophin did not increase the conversion of radioactive deoxycorticosterone to total 11-oxygenated steroids (corticosterone+ 11-dehydrocorticosterone). It is unlikely therefore that ACTH stimulates 11 β-hydroxylation.

Data indicate that the ratio of deoxycorticosterone to total 11-oxygenated steroids (corticosterone +11-dehydrocorticosterone) is characteristic for each cell type, and that this ratio will be relatively independent of ACTH stimulation or the amount of pregnenolone substrate available.

Basal androstenedione outputs were similar for both types of cell, and ACTH stimulation was very small, being slightly greater for zona fasciculata than for zona reticularis cells.

The contribution of the zona reticularis cells to the basal output of any steroid by the cells of the inner two zones of the adrenal cortex of the rat was relatively small (20% for deoxycorticosterone and 10% for corticosterone) and was even less after stimulation by ACTH. Unless a specific stimulus can be found, therefore, a significant role for the zona reticularis cannot yet be established.
PERIPHERAL CONCENTRATIONS OF PROGESTERONE, CORTISOL, ALDOSTERONE, SODIUM AND POTASSIUM IN THE PLASMA OF THE TADMIT EWE DURING PREGNANCY AND PARTURITION
Authors: BOULFEKHAR LOUISA , BRUDIEUX ROGER
Published: December 2008

The peripheral blood concentrations of progesterone, cortisol, aldosterone and electrolytes were measured simultaneously in 16 multiparous ewes of the Tadmit Algerian breed during pregnancy and parturition.

Plasma progesterone concentrations were similar to those of the luteal phase of the oestrous cycle during the first third of gestation. Between 60 and 135 days after mating, the levels of plasma progesterone increased steadily to values eight times those found in early pregnancy. However, no change was observed from days 43 to 28 before parturition. Mean progesterone concentrations declined during the 17 days preceding lambing, decreasing more quickly during the last 3 days.

Pregnancy did not increase the levels of plasma cortisol and the mean values during pregnancy did not exceed 0·5 μg/100 ml until 90 days after mating. It then tended to decrease between days 57 and 17 before parturition, before rising slightly on both day 7 and on the day of lambing.

Concentrations of plasma aldosterone were low during early pregnancy (about 2 ng/100 ml). Thereafter, as with progesterone, they rose from days 58 to 43, did not change from days 43 to 28 and increased again until maximum levels were reached 17 days prepartum and then levels decreased sharply until 7 days before lambing. At this stage, progesterone levels continued to decrease during the last 7 days while aldosterone concentrations once more increased.

Sodium and potassium concentrations changed little during pregnancy, although the sodium: potassium ratio tended to increase during the last 17 days of pregnancy. It is suggested that changes in the levels of plasma aldosterone during gestation in the ewe are the result of the competitive inhibition of aldosterone by progesterone at a renal level and that the rise of aldosterone during the last few days of pregnancy is largely due to the stimulation of renin substrate production by oestrogens whose values are high at this period.
DIURNAL VARIATIONS OF PLASMA PROLACTIN IN GROWING SHEEP UNDER TWO LIGHTING RÉGIMES AND THE EFFECT OF PINEALECTOMY
Authors: BROWN WENDY B. , FORBES J. M.
Published: December 2008

The role of the pineal gland in mediating the stimulatory effect of long daylength on blood levels of prolactin was investigated in 24 growing castrated sheep. Eight were pinealectomized, eight were sham-pinealectomized and eight remained as unoperated control animals. After a preliminary period with 12 h light:12 h darkness (12L: 12D) pairs of similar sheep were allocated to photoperiods of 16L: 8D or 8L: 16D for 15 weeks. Each animal was individually fed at the same level as its partner exposed to the other daylength. Blood samples were taken weekly by jugular venepuncture. On two occasions, once in the preliminary period (12L: 12D) and again 41 days after the start of the subsequent photoperiods, samples were taken through indwelling jugular catheters at frequent intervals for 24 h. The plasma samples were assayed for prolactin by radioimmunoassay and concentrations were higher in samples taken by jugular puncture.

There was a consistent positive effect of daylength on plasma prolactin in sheep with pineal glands that did not occur in pinealectomized sheep. In contrast, pinealectomy did not block the marked rise in prolactin that occurred at dusk. It appears that the effect of the photoperiod on levels of plasma prolactin throughout the day and night is not mediated by the same mechanism as that which controls the surge of prolactin at dusk in the sheep.
FREE AND PROTEIN-BOUND TRI-IODOTHYRONINE IN THE SERUM OF VITAMIN A-DEFICIENT RATS
Authors: GARCIN H. , HIGUERET P.
Published: December 2008

Tri-iodothyronine (T3) transport in the serum of rats on a vitamin A-deficient diet was studied by electrophoresis after the incubation of serum samples with radioactive T3. The level of serum free tri-iodothyronine (fT3) was measured by radioimmunoassay after serum chromatography on Sephadex LH-20 gel. In the serum of control rats a major part of the radioactivity was bound to the albumin zone (61%) and a minor part to the prealbumin zone (32%). In the serum of vitamin A-deficient rats a larger amount of radioactivity was bound to the postalbumin zone; the lower the level of vitamin A in serum, the greater was the radioactivity in this zone of the electrophoretogram. In these animals there was also a negative correlation between the serum vitamin A and the fT3. There was also a positive correlation between the radioactivity bound to the postalbumin zone and the fT3. The possible causes and effects of these modifications in vitamin A-deficient rats are discussed.
THE PROLIFERATIVE ACTION OF OESTRIOL
Authors: LEE AUDREY E.
Published: December 2008

Daily injections of oestriol, spanning a wide dose range, produced mitotic responses in the uterine luminal epithelium of mice. At the higher doses the response was comparable to that obtained with oestradiol. The maximum response occurred on day 1, after which mitosis was significantly reduced on days 2 and 3. This reduction in mitosis following an initial peak was seen at all doses and was not therefore consequent on a critical cell number being reached. Proliferation was also induced in the basal epithelium of the vagina, though to a lesser extent. Oestriol and progesterone together stimulated DNA synthesis and mitosis in the epithelium of the mammary gland.
INTERACTION OF SPIRONOLACTONE WITH OESTRADIOL RECEPTORS IN CYTOSOL
Authors: LEVY J. , BURSHELL A. , MARBACH M. , AFLLALO L. , GLICK S. M.
Published: December 2008

The role of spironolactone in the aetiology of gynaecomastia was examined in terms of its ability to bind to the oestrogen receptor in cytosol, to cause specific oestrogenic effects in the absence of endogenous oestrogen and to be antioestrogenic in the presence of oestradiol. Tamoxifen, a non-steroidal antioestrogen, was chosen as an internal standard for comparison.

Spironolactone and tamoxifen competitively inhibited the binding of oestradiol-17β to its receptor in uterine and mammary cytosol, with inhibition constants of 2 × 10−5 and 1 × 10−7 respectively.

To measure oestrogenic or antioestrogenic effects of the drugs five indices believed to be specific markers for oestrogen action were studied: uterine to body weight ratio, uterine protein content, oestradiol receptor in cytosol, progesterone receptor in cytosol and uterine peroxidase activity.

Spironolactone, when administered for 3 successive days (40 μg/day) to immature female rats, increased all of the five indices of oestrogen agonistic activity. The oestrogenantagonistic properties of the drug were evaluated by comparing the oestradiol-injected group (5 μg) to the oestradiol + spironolactone-injected group. A decrease was noted in all indices measured except for progesterone receptors in cytosol. Spironolactone appeared to be very similar to tamoxifen in its action both as an oestrogen and as an antioestrogen.

The antioestrogenic effect of spironolactone cannot be explained by previously proposed mechanisms of action for the drug such as decreased synthesis of testosterone or inhibition of dihydrotestosterone binding to its receptor. These results suggest that spironolactone-induced gynaecomastia may be modulated by its action at both the oestrogen and dihydrotestosterone receptor in cytosol.
IN-VITRO SYNTHESIS OF ANDROGEN FROM PREGNENOLONE IN THE TESTES OF THE GOAT (CAPRA HIRCUS) AND IDENTIFICATION OF 5-PREGNENE-3β,17α,20α-TRIOL AS AN INTERMEDIATE IN THE METABOLIC PATHWAY OF PREGNENOLONE
Authors: MORI MAKOTO , MATSUKURA SACHIKO , KAWAKURA KAZUHIKO , TAMAOKI BUN-ICHI
Published: December 2008

When [4–14C]pregnenolone was aerobically incubated in vitro in the presence of NAD+ and NADPH with cell-free homogenates of testicular tissue of adult domestic goats (Capra hircus), progesterone, 17α-hydroxypregnenolone, 17α-hydroxyprogesterone, 17α,20α-dihydroxy-4-pregnen-3-one, dehydroepiandrosterone, androstenedione and testosterone were identified as its known metabolites. Time-course studies on this metabolism showed that the production of 17α,20α-dihydroxy-4-pregnen-3-one and testosterone constantly increased up to the end of incubation, suggesting that these are both end-products of pregnenolone metabolism in this system. The other metabolites behaved as intermediates and were ultimately converted, in part, to testosterone by the testicular homogenates, indicating that testosterone was synthesized through both 4-ene and 5-ene-pathways. Furthermore, besides these metabolites, 5-pregnene-3β,17α,20α-triol was also identified as an intermediary metabolite, formed from pregnenolone through 17α-hydroxypregnenolone in the presence of NADPH, and further convertible into 17α,20α-dihydroxy-4-pregnen-3-one by the microsomal fraction and into 17α-hydroxypregnenolone by the cytosol fraction in the presence of NAD+ and NADP It was not, however, significantly transformed into C19-steroids. Furthermore, 17α,20α-dihydroxy-4-pregnen-3-one, which was formed either from 5-pregnene-3β,17α,20α-triol or from 17α-hydroxyprogesterone, remained almost unchanged without conversion to C19-steroids when incubated with the caprine testicular homogenates.
TIMING OF TERMINATION OF NOCTURNAL PROLACTIN SURGES IN PREGNANT RATS AS DETERMINED BY THE NUMBER OF FETUSES
Authors: YOGEV LEAH , TERKEL JOSEPH
Published: December 2008

In female rats bearing an average litter of 10 ± 0·28 fetuses, pituitary prolactin is secreted in a pattern of two daily surges during the first 10 days of pregnancy only. When the number of fetuses was experimentally reduced, prolactin surges continued for a longer period and pregnancy was correspondingly lengthened. The relationship found between a reduced number of fetuses, and delay in termination of prolactin surges further supports the view that, during pregnancy, rat placental lactogen exerts a major influence in inhibiting secretion of prolactin by the maternal pituitary gland. The constant relationship found in all groups between termination of nocturnal surges of prolactin and parturition indicates that it is the interval between implantation and termination of prolactin surges which is prolonged in female rats with small litters.
DIFFERENTIAL SENSITIVITY OF PROLACTIN RELEASE TO DOPAMINE AND THYROTROPHIN-RELEASING HORMONE IN INTACT AND PITUITARY STALK-SECTIONED RHESUS MONKEYS
Authors: NORMAN R. L. , QUADRI S. K. , SPIES H. G.
Published: December 2008

The effects of dopamine and thyrotrophin-releasing hormone (TRH) on prolactin release was studied in 14 intact and six pituitary stalk-sectioned (SS) female rhesus monkeys (Macaca mulatta). Baseline prolactin values were ninefold higher in SS animals (149 ± 16 ng/ml) than in intact animals (16 ± 1 ng/ml).

Prolactin release after intravenous administration of TRH in doses of 0,125,250, 500 and 1000 ng revealed that SS monkeys were more sensitive to the prolactin-releasing activity of this tripeptide than were intact animals. A significant (P < 0·05) increment in serum prolactin was observed in SS animals after injection of 125 ng TRH whereas 250 ng was required to raise prolactin levels in the circulation of intact animals significantly (P <0·05). Furthermore, at each comparable dose level of TRH, the increment in serum prolactin was distinctly greater in SS animals than in intact monkeys.

Infusion of dopamine at the rate of 10 μg/kg body weight per min significantly (P <0·05) lowered prolactin levels within 60 min in intact animals and no further decline was observed with 20 or 40 μg dopamine. Serum prolactin concentrations were not affected by saline infusion or by 5 μg dopamine. Infusion of dopamine at the rate of 10 μg/kg body wt per min also resulted in significant (P <0·01) suppression of serum prolactin in SS animals. This prolactin decrease was apparent within 40 min. Prolactin release after 500 ng TRH was less in these dopamine-treated SS monkeys than after an infusion of saline. Higher doses of dopamine (20 and 40 μg) did not cause a further decrease in basal serum prolactin concentrations, but these two dopamine treatments blocked the increase in prolactin elicited by 500 ng TRH.

The results suggest that the removal of hypothalamic influence, possibly related to the effects of dopamine, renders the pituitary gland more sensitive to the prolactin-releasing action of TRH.
REGULATION BY THE PITUITARY GLAND OF CIRCADIAN RHYTHMS IN THE HAMSTER
Authors: ZUCKER IRVING , CRAMER CATHERINE P. , BITTMAN E. L.
Published: December 2008

Locomotor activity of male hamsters was recorded during long-term exposure to constant light (LL), constant darkness (DD) and during entrainment (modification of a circadian rhythm) to a 14 h light: 10 h darkness photoperiod (14L: 10D). In LL the period of the activity cycle was substantially longer in hypophysectomized than in control animals. This difference persisted during tests in DD. Although hypophysectomy reduced the duration of the active phase in some hamsters, overall the difference between the groups was not significant. The phase angle of onset of activity in 14L: 10D was not affected by hypophysectomy. Hypophysectomized female hamsters tested in DD had activity rhythms whose periods were longer than those of control animals; they were also significantly less active than corresponding controls during the first 4 h of the subjective night but the duration of the active phase did not differ significantly between the groups. These results suggest that hormones of the pituitary-gonadal axis modulate the period of circadian oscillation.
EFFECT OF ADRENALECTOMY OR CASTRATION ON THE INHIBITION OF GONADOTROPHIN SECRETION INDUCED BY HYPERPROLACTINAEMIA IN THE ADULT MALE RAT
Authors: McNEILLY A. S. , SHARPE R. M. , FRASER H. M.
Published: December 2008

To investigate the role of adrenal and gonadal steroids in the long-term suppression of gonadotrophin secretion induced by prolactin the effects of adrenalectomy or castration on the serum and pituitary levels of LH, FSH and prolactin and the hypothalamic content of LH releasing hormone (LH-RH) have been studied in adult male rats with hyper prolactinaemia produced by the transplantation of pituitary glands under the kidney capsule.

Levels of LH and FSH in serum were significantly suppressed in all intact pituitary-grafted rats. Adrenalectomy on the day of pituitary implantation or 20 days later did not affect this suppression. However, castration on days 0,28 or 49 after pituitary grafting resulted in a rise in levels of FSH in serum indistinguishable from that in control rats. While the rise in levels of LH after castration on day 0 was the same as the controls, this increase was significantly reduced 2 days after castration on days 28 and 49 after pituitary grafting.

Castration resulted in an increase in the pituitary content of LH and a reduction in the hypothalamic content of LH-RH but no change in the pituitary content of FSH. Hyperprolactinaemia did not appear to affect these responses.

The present results showed clearly that the gonad but not the adrenal must be present for prolactin to exert an inhibitory effect on gonadotrophin secretion.
DIURNAL VARIATION IN THE INDUCIBILITY OF LUTEAL 20α-HYDROXYSTEROID DEHYDROGENASE IN PREGNANT RATS
Authors: HICKMAN-SMITH DAVID , KUHN N. J.
Published: December 2008

Luteolysis was induced in rats during late pregnancy by fetoplacental removal, and was monitored by the increased activity of luteal 20α-hydroxysteroid dehydrogenase (20α-OHSDH). The extent of enzyme induction over a given length of time varied according to the time of day at which the fetuses and placentae were removed, 11.00 and 21.00 h appearing to give optimal and minimal enzyme activities respectively. The 20α-OHSDH was more readily induced on day 19 than on day 18.
CHANGES IN CORTISOL BINDING AND METABOLISM DURING NEONATAL DEVELOPMENT IN THE GUINEA-PIG
Authors: DALLE M. , EL HANI A. , DELOST P.
Published: December 2008

The metabolic clearance rate and the binding of cortisol in plasma of male and female guinea-pigs were estimated at five stages between birth and weaning. The metabolic clearance rate for cortisol remained low in both sexes until day 10 post partum but increased to adult values by day 20. The level of free cortisol in plasma and the cortisol binding capacity of the plasma were higher at birth than on day 10 post partum; the values found on day 20 were similar to those of the adult guinea-pig. Surgical stress increased levels of cortisol in plasma on day 20 but not at birth.
PARTIAL PURIFICATION OF LOW MOLECULAR WEIGHT NON-SUPPRESSIBLE INSULIN-LIKE ACTIVITY FROM HUMAN PLASMA: DEMONSTRATION OF THE PRESENCE OF MULTIPLE FORMS
Authors: COCKERILL P. N. , CORNELL H. J. , HERINGTON A. C.
Published: December 2008

An alternative procedure for the separation of insulin-like growth factors from plasma, avoiding the harsh conditions of acid–ethanol extraction, suggested that several factors which have activity in the isolated rat adipocyte assay may be present.

The initial step consisted of ion-exchange chromatography of an enriched Cohn fraction (IV-1) on SP-Sephadex using ammonium acetate buffers. The major activity appeared in a fraction eluted at pH 7·1–9·4. When this fraction was subjected to gel filtration on Sephadex G-75 in 1% formic acid, most of the activity was recovered in a fraction of molecular weight of 5000–8000, but up to 25% of the activity applied remained in a much higher molecular weight form. The active material of low molecular weight was recovered at a considerably greater yield compared with that obtained by the more conventional acid–ethanol extraction followed by gel filtration on Sephadex G-75. The fraction was further purified by DEAE–Sephadex chromatography and isoelectric focussing. Non-suppressible insulin-like activity (NSILA) of pI 4·8 and 6·0 were the major species detected. The results were in contrast with those obtained using acid–ethanol extraction of the Cohn fraction, where the major species were of pI 6·0 and 8·0. The presence of multiple forms of NSILA would thus appear to justify the use of alternative methods of purification.
CONCENTRATIONS OF LUTEINIZING HORMONE IN THE SERUM OF MALE MICE AFTER SHORT-TERM AGGRESSIVE INTERACTION
Authors: BARKLEY M. S.
Published: December 2008

Adult male mice were castrated and implanted with silicone elastomer capsules containing either testosterone or sesame oil. Brief exposure to a strange male opponent depressed levels of LH in castrated animals treated with oil, but did not add to the suppressive effects of testosterone on the concentration of LH in serum. Accessory organ weights were not affected by brief aggressive encounters, nor were levels of testosterone in serum altered in response to repeated encounters with a submissive (olfactory bulbectomized) male opponent. The observation that exposure to a strange male conspecific suppressed secretion of gonadotrophin in the absence of gonadal androgen(s) suggests that stress-responsive, antigonadotrophic factors can inhibit pituitary-gonadal function. A mechanism whereby gonadotrophin secretion may be suppressed in the androgen-deprived state is discussed.
CHROMATOGRAPHIC CHARACTERIZATION OF ADRENOCORTICOTROPHIN IN HUMAN PLASMA
Authors: RATTER SALLY J. , LOWRY P. J. , BESSER G. M. , REES LESLEY H.
Published: December 2008

A chromatographic procedure has been developed for the characterization of ACTH- and lipotrophin- (LPH) related peptides in human plasma under acid-dissociating conditions to minimize artifacts of protein binding. The recovery and sensitivity of this method permits identification of ACTH at normal physiological levels in the circulation. Plasma profiles obtained from normal subjects and patients with pituitary dependent Cushing's disease, Addison's disease and Nelson's syndrome showed only one significant peak of ACTH activity eluting in the position of purified native human 1–39 ACTH. However, the plasma profiles obtained from all the patients with the ectopic ACTH syndrome demonstrated a second peak of immunoreactive larger-molecular-weight ACTH and in some plasma samples this was the only form of ACTH observed. This larger-molecular-weight ACTH eluted midway between the void volume and 1–39 ACTH and co-eluted with a protein marker of molecular weight 22 000.
EFFECT OF OESTRADIOL ON THE POST-PARTUM RAT UTERUS: PEROXIDASE ACTIVITY AND COLLAGEN BREAKDOWN
Authors: WOESSNER J. F. , RYAN JANET N.
Published: December 2008

Treatment of parturient rats with 100 μg oestradiol/day caused a significant retardation of uterine involution and collagen breakdown. The post-partum uterus had a peroxidase activity of 180 μmol H2O2 reduced/min per uterus. Treatment with oestradiol caused an eight- to tenfold increase in this activity within 3–4 days. Treatment of rats with 4 mg cortisol/day commencing 3 days prepartum had no effect on uterine peroxidase activity but it blocked the oestradiol-induced increase in peroxidase. Cortisol had no effect on collagen breakdown and did not reverse the inhibition of collagen breakdown produced by oestradiol. It is postulated that the effects of oestradiol on peroxidase activity are mediated by uterine epithelial cells but that oestradiol effects on collagen breakdown may be mediated by another cell type.
HORMONAL REGULATION OF FOLLICLE-STIMULATING HORMONE RECEPTORS IN THE TESTES OF JAPANESE QUAIL
Authors: TSUTSUI KAZUYOSHI , ISHII SUSUMU
Published: December 2008

The effects of gonadotrophins and testosterone on the binding of 125I-labelled rat FSH to a testicular homogenate of hypophysectomized Japanese quail have been studied. Hypophysectomy resulted in rapid decrease in the binding of FSH per testis but did not change the binding per unit testicular weight, suggesting a decrease in FSH binding per Sertoli cell. Injections of NIH-FSH-S12 to hypophysectomized birds (100 pg/day) for 5 days induced hypertrophy of Sertoli cells and 2·2-fold increase in the binding of FSH per Sertoli cell. Injections of testosterone to hypophysectomized birds (5·0 mg/day) for 5 days also increased the binding of FSH per Sertoli cell 2·3-fold, but did not change the cell size. Combined administration of FSH and testosterone induced 4·4-fold increase in the binding of FSH per Sertoli cell and also marked hypertrophy. The Scatchard plot analysis of the binding of FSH to the testicular preparation of hypophysectomized birds treated simultaneously with FSH and testosterone showed that the number of the binding sites, but not the affinity of the binding, was increased by the hormone treatment. Synergistic action of FSH and testosterone was observed in the increase of not only the number of the FSH binding sites but also in testicular weight and the number of spermatogonia and spermatocytes. These results indicated that FSH receptors in the testes of Japanese quail are regulated by FSH and testosterone. It is suggested that FSH acting synergistically with testosterone increases the sensitivity of the testis to FSH itself by increasing FSH receptors. This self-potentiation mechanism may enable rapid testicular development in photostimulated birds and mammals at puberty.
RELATIONSHIP BETWEEN THE DECIDUAL RESPONSE AND OVARIAN STEROIDOGENESIS IN THE UNILATERALLY OVARIECTOMIZED PSEUDOPREGNANT RAT
Authors: TERRANOVA P. F.
Published: December 2008

The influence of the decidual cell reaction (DCR) on luteal and non-luteal ovarian steroidogenesis was ascertained on day 8 of pseudopregnancy in unilaterally ovariectomized rats. Whether a 'local' interaction existed between the DCR and ovarian steroidogenesis was of particular interest. Holtzman rats were subjected to unilateral ovariectomy and after exhibiting two successive oestrous cycles, they were rendered pseudopregnant by cervical stimulation at oestrus (day 1). On day 5 of pseudopregnancy, rats were subjected to a unilateral stimulus to induce a decidual cell reaction (ipsilateral or contralateral to the remaining ovary) or to sham-operation. On day 8 of pseudopregnancy, they were killed by decapitation and serum was stored for radioimmunoassay of progesterone, androgen, oestradiol, prolactin, FSH and LH. Also the corpora lutea and non-luteal portion of the ovary (NLO) were incubated for 2 h in Krebs–Ringer bicarbonate buffer. Steroid concentrations were determined in the corpora lutea and NLO before and after incubation and in the incubation media.

No differences were observed between groups (no DCR, ipsilateral DCR, contralateral DCR) in the serum concentrations of progesterone, androgen, FSH, LH or prolactin. However, serum levels of oestradiol were significantly lower than those levels in rats lacking DCR. No 'local' steroidogenic effect of the DCR was observed in the corpora lutea or NLO; although it appeared that the DCR could stimulate luteal progesterone production since corpora lutea from rats with ipsilateral DCR produced more progesterone in vitro than rats lacking DCR (but not than rats with contralateral DCR). The presence of a DCR was associated with lower levels of oestradiol in serum, corpora lutea and NLO and also with lower in-vitro production of oestradiol by NLO and corpora lutea than unilaterally ovariectomized rats lacking DCR. Since androgen levels in serum, corpora lutea and NLO were not altered by the presence of a DCR, it seems plausible that the DCR may alter oestrogen synthesis (aromatase) in the ovary.
RELEASE, DISTRIBUTION AND HALF-LIFE OF α-MELANOTROPHIN IN THE RAT
Authors: WILSON J. F. , HARRY FRANCES M.
Published: December 2008

Concentrations of α-melanotrophin in the plasma of anaesthetized rats were measured by radioimmunoassay at intervals of 2–10 min. Although significant increases of three to ten times in the concentration of α-melanotrophin occurred over periods of 15–35 min, levels of hormone could also be stable for periods of greater than 1 h. The data did not indicate separate secretory episodes but rather a continuous release of α-melanotrophin by the pituitary gland. A very rapid pulsatile secretion operating over periods of less than 5 min cannot be excluded.

Intravenous injection of synthetic α-melanotrophin was followed by a biexponential decline in levels of hormone in plasma indicating a rapid distribution to the extracellular fluid and a slower elimination by metabolism. The apparent volume of distribution of α-melanotrophin was 210 ml/kg, the half-life for elimination 7·1 min and the estimated clearance 1·55 nmol/day per kg.
TAMOXIFEN SUPPRESSES BOTH THE GROWTH OF PROLACTIN-SECRETING PITUITARY TUMOURS AND NORMAL PROLACTIN SYNTHESIS IN THE RAT
Authors: DE QUIJADA M. , TIMMERMANS H. A. T. , LAMBERTS S. W. J.
Published: December 2008

The effect of administering the antioestrogenic drug, tamoxifen, on the growth of the pituitary tumour 7315a in the rat was studied. This tumour is induced by the administration of oestrogen. When administered early after the implantation of the tumour, tamoxifen prevented its growth completely but when treatment was delayed until a later stage of its development, 20 μg tamoxifen/100 g body wt each day for 7–12 days stopped further tumour growth, while 200 μ/100 g body wt each day reduced the size of the tumours. These effects of tamoxifen on tumour growth were accompanied by a decrease in the level of prolactin in the circulation, if the treatment was started at an early stage of tumour development and if the high dose of tamoxifen was administered. Bromocriptine either when given alone or together with tamoxifen was unable to inhibit growth and secretion of prolactin by these rat pituitary tumours. The high plasma concentrations of prolactin in the tumour-bearing rats are known to produce atrophy of the pituitary gland of the host and to decrease the synthesis and release of prolactin. Despite the inhibitory effect of tamoxifen on both tumour size and plasma levels of prolactin, the ability of the pituitary glands of these animals to synthesize prolactin remained suppressed. It was concluded that tamoxifen has a dual effect on this model of a transplantable pituitary tumour that secretes prolactin in the rat; it prevents and/or inhibits tumour growth and it has an inhibitory effect on the synthesis of prolactin by the pituitary gland.
EFFECT OF BROMOCRIPTINE, ERGOTAMINE AND OTHER ERGOT ALKALOIDS ON THE HORMONE SECRETION AND GROWTH OF A RAT PITUITARY TUMOUR
Authors: PRYSOR-JONES R. A. , JENKINS J. S.
Published: December 2008

The effect of bromocriptine on hormone secretion and the growth of the prolactin- and growth hormone (GH)-secreting rat pituitary tumour of the GH3 cell line has been compared with that of ergotamine and other ergot alkaloids. Bromocriptine in doses ranging from 1 to 20 mg/kg had no effect on tumour growth or on the excessive secretion of GH by the tumour; prolactin concentrations were reduced only by the highest dosage of the drug. Similarly the tumour was resistant to the administration of ergocryptine, ergocornine and the synthetic ergolines, lergotrile and CH 29–717. In contrast, ergotamine reduced secretion of both GH and prolactin and considerably inhibited the growth of the tumour. Experiments in vitro showed that ergotamine inhibited DNA synthesis of the tumour cells and decreased hormone secretion. It was concluded that ergotamine had a direct inhibitory action on the GH3 cell tumour which was not mediated through the dopaminergic mechanisms.
EFFECT OF OVARIECTOMY AT BIRTH ON THE REGULATION OF SEBACEOUS GLANDS IN RATS
Authors: TOH YEE CHU
Published: December 2008

Inbred Sprague–Dawley rats were ovariectomized within 24 h of birth. Sham-operated and untreated male and female rats were also included for comparison. At the age of 80 days, the secretion rate of sebum was assessed from the amount of skin-surface lipids that could be extracted by acetone and which had been produced during 2 days. There were no differences in sebum secretion, when expressed both in relationship to body weight and to surface area of the body, when rats ovariectomized at birth, sham-operated and intact female rats were compared. The removal of the ovaries within 24 h of birth increased the body weight, however. Although the weights of the pituitary, thyroid and adrenal glands, when corrected for body weight, were significantly smaller in rats ovariectomized at birth than in the sham-operated or intact female rats, there were no statistically significant differences in the absolute weights of these endocrine organs between neonatally spayed rats and sham-operated animals. The uterus became atrophic in the absence of ovaries. It has been concluded that the presence or absence of ovaries in the early stage of life had no effect on the activity of the sebaceous glands.
EFFECTS OF OESTRADIOL AND PROGESTERONE ON THE CONCENTRATION OF α2-MACROGLOBULIN IN THE SERA OF INJURED MALE AND FEMALE RATS
Authors: BELL S. C.
Published: December 2008

The effects of ovarian hormones on the synthesis of α2-macroglobulin in response to injury were investigated. After injection of turpentine to provoke synthesis of α2-macroglobulin, the mean concentrations of this protein in serum were lower in intact female than in male rats. Sera from injured ovariectomized rats contained levels of α2-macroglobulin similar to those of injured male animals. Administration to ovariectomized animals of oestradiol or oestradiol plus progesterone substantially reduced the levels of α2-macroglobulin produced in response to injury. Administration of progesterone only resulted in a small increase in the response of ovariectomized animals to injury. Oestradiol and progesterone had no effect on the response of male rats to injury. These findings suggest that only in the female rat can these steroid hormones, especially oestradiol, regulate the synthesis of α2-macroglobulin in response to tissue injury.
PLACENTAL LACTOGEN IN THE GOAT IN RELATION TO STAGE OF GESTATION, NUMBER OF FETUSES, METABOLITES, PROGESTERONE AND TIME OF DAY
Authors: HAYDEN T. J. , THOMAS C. R. , SMITH SUSAN V. , FORSYTH ISABEL A.
Published: December 2008

Placental lactogen has been measured in goats throughout pregnancy by radioreceptor assay of prolactin-like activity. Lactogenic activity, which is not prolactin, increased from less than 5 nmol/l in week 8 to 27 nmol/l by week 16. There was no further change until term. Plateau concentrations (week 16 to term) were highest in animals carrying triplets, 49·5 nmol/l. There were marked fluctuations in placental lactogen over a 24 h period. These short-term fluctuations were not related to changes in glucose, non-esterified fatty acids or, in two animals, progesterone. However, there was a negative correlation between mean concentrations of placental lactogen and glucose in plasma of 20 goats sampled over a 24 h period between weeks 15 and 20 of gestation. There was no difference in placental lactogen concentration from week 16 to term between goats in their first and second pregnancies although the normal period of increase in placental lactogen was delayed by some 3 weeks in goats in their second pregnancy. In hemimastectomized goats, hypophysectomy on day 60 did not affect placental lactogen but daily treatment with bromocriptine (5 mg/day) from day 60 to day 120 blocked the normal rise in concentration.