bluuebunny/crossref_metadata_2025 huggingface dataset:
PLASMA PROLACTIN AND PROGESTERONE RESPONSES TO MATING ARE ALTERED IN AGED RATS
Authors: HENDRICKS S. , BLAKE C. A.
Published: December 2008

The effects of varying amounts of copulatory stimulation on patterns of plasma concentrations of prolactin and progesterone were evaluated in 3- and 12-month-old female rats. The 12-month-old group included rats which still exhibited oestrous cycles and rats in persistent vaginal oestrus (PVO). The extent of copulatory stimulation was defined by the number of intromissions received during mating: ≤5,15 or > 50. Blood samples were drawn over the 8 days after mating through a cannula inserted into the right external jugular vein. Plasma from the samples was assayed for prolactin and progesterone. In aged but still cyclic rats, pregnancy rates were positively correlated with the number of intromissions received during mating. Only one rat in PVO became pregnant. All animals which became pregnant and rats in PVO which, after mating, exhibited a disruption of the pattern of PVO, showed the nocturnal surge of plasma prolactin characteristic of pregnant and pseudopregnant rats. While these surges persisted until day 8 after mating in pregnant animals, they were absent by this time in the rats in PVO. Prolactin surges were present in some but not all of the aged rats which did not become pregnant. Progesterone concentrations were raised in all pregnant animals except the one pregnant rat in PVO and, while not related to the number of intromissions, concentrations were higher 8 days after mating in young compared with those in aged pregnant rats. Plasma progesterone was low in rats in PVO regardless of disruption of the pattern of PVO. We have concluded that the failure of limited copulatory stimulation to induce pregnancy in older rats results, at least in part, from its failure to initiate nocturnal prolactin surges. Nevertheless, our data suggest that matings which are not experimentally limited should provide ample stimulation to establish such surges. Although reduced plasma concentrations of prolactin and progesterone at pro-oestrus and reduced plasma progesterone through part of gestation may contribute to decreasing fertility in aged rats, other unidentified factors appear to be involved in mediating the capacity of extensive copulatory stimulation to induce pregnancy in these animals.
ELECTROPHYSIOLOGICAL RECORDINGS FROM OXYTOCINERGIC NEURONES DURING SUCKLING IN THE UNANAESTHETIZED LACTATING RAT
Authors: SUMMERLEE A. J. S. , LINCOLN D. W.
Published: December 2008

A method is described for making extracellular recordings of the spontaneous activity of single hypothalamic neurones in unanaesthetized, freely moving, lactating rats using chronically implanted micro-wire electrodes. Extracellular recordings taken from individual neurones were maintained for periods of between 1 and 12 days. These records were not affected by any normal movement of the animal. As several micro-wires were implanted into each animal it was possible to make simultaneous recordings from several different hypothalamic sites in the same animal. Some recordings were identified as those from magnocellular neurones in the paraventricular nucleus on the basis of antidromic invasion after electrical stimulation of the neurohypophysis.

Milk ejection in response to the prolonged sucking of ten or more pups was intermittent, and individual milk ejections recurred at intervals of 2–10 min throughout each period of nursing. The rise in intramammary pressure at milk ejection was associated with a vigorous extensor response from the pups. This was monitored by radar to provide an index of milk ejection in the unanaesthetized rat.

Eleven antidromically identified neurones were recorded through 321 milk ejections. Eight of these neurones displayed a transient (2–6 s) and very substantial acceleration in discharge at the time predicted for oxytocin release, i.e. 10–12 s before milk ejection. The background discharge of these cells was 0·1–2·6 action potentials/s; this increased to 16–50 action potentials/s during the brief period of accelerated activity. Twenty-five neurones were studied during 365 milk ejections in rats which did not have a stimulating electrode implanted in the neurohypophysis. Thirteen of these neurones displayed a burst of high frequency discharge before each milk ejection, similar to that described for the antidromically identified neurones. Two of the non-responsive cells displayed a phasic pattern of discharge, characteristic of vasopressinergic neurone discharge recorded in anaesthetized rats.

These observations of putative oxytocinergic neurones in unanaesthetized, freely moving rats are identical with those previously made on anaesthetized rats, and establish that the high frequency burst of electrical activity displayed by magnocellular neurones some 10–12 s before milk ejection is responsible for oxytocin release under normal physiological circumstances.
2-HYDROXYOESTRADIOL INHIBITS PROLACTIN RELEASE FROM THE SUPERFUSED RAT PITUITARY GLAND
Authors: LINTON ELIZABETH A. , WHITE NICKI , LIRA DE TINEO OFELIA , JEFFCOATE S. L.
Published: December 2008

The effects of 2-hydroxyoestradiol (2OH-OE2), dopamine, oestradiol-17β and 2OH-OE2 plus dopamine on prolactin and LH release from the male rat pituitary gland were examined in vitro.

2-Hydroxyoestradiol reduced prolactin secretion by 51% at 10−10 mol/l and by 34% at 10−7 mol/l, while oestradiol-17β had no effect at these doses. Dopamine alone (5 × 10−7 mol/l) decreased prolactin released by 58%, 2OH-OE2 plus dopamine produced a similar inhibition of 60%.

No significant effect on LH release was observed throughout.
CONCENTRATION AND RELATIONSHIP TO PROGESTERONE OF PROGESTERONE-BINDING GLOBULIN IN PREGNANT GUINEA-PIGS: MEASUREMENT BY PROGESTERONE TRACER BINDING ASSAY
Authors: EVANS J. J. , WHITE FELICITY J. , SIN IRIS L.
Published: December 2008

A single-point progesterone tracer binding assay (TBA) was developed to measure the concentration of progesterone-binding globulin (PBG) in the serum of pregnant guinea-pigs. Tritiated progesterone was added to dilutions of a reference serum, the percentage bound calculated and a standard curve constructed. The amount of progesterone tracer bound to serum samples was determined, and the concentration of binding protein in the sample relative to the reference was calculated. The molar concentration in the reference serum was determined by Scatchard analysis. The TBA could readily process 30 samples per day. There was a rapid rise in PBG concentrations between days 15 and 20 of gestation, in parallel with progesterone concentrations. The molar ratio of PBG: progesterone was approximately 10: 1 after this time, until about day 45 when there was an increase in ratio.
FETAL AND MATERNAL OVINE PLACENTAL LACTOGEN DURING HYPERGLYCAEMIA, HYPOGLYCAEMIA AND FASTING
Authors: BRINSMEAD M. W. , BANCROFT B. J. , THORBURN G. D. , WATERS M. J.
Published: December 2008

Hyperglycaemia was produced in chronically catheterized fetal lambs and pregnant ewes by the infusion of glucose into the fetus. Plasma concentrations of placental lactogen did not change significantly in either fetal or maternal circulations. Fetal and maternal hypoglycaemia was induced by administration of insulin to the fetus and ewe separately. Plasma concentrations of placental lactogen in the fetus did not change significantly but maternal plasma concentrations fell slightly after hypoglycaemia in either fetus or ewe. Plasma concentrations of placental lactogen rose in both the ewe and fetus during prolonged fasting of the ewe. These results neither confirm nor refute a role for placental lactogen in intermediary metabolism of the pregnant ewe and fetus but glucose concentration alone is unlikely to be a significant factor in the control of secretion of this hormone.
DYNAMICS OF PROGESTERONE METABOLISM IN THE PSEUDOPREGNANT RAT
Authors: ROBINSON J. , MERRY B. J. , LIGHTFOOT M. E. , HALL A. K.
Published: December 2008

The characteristics of the disappearance of progesterone and 20α-dihydroprogesterone from blood were examined in rats made pseudopregnant by administration of gonadotrophins. Measurement of the disappearance of [3H]progesterone from blood indicated that progesterone metabolism can be represented by a two-compartment model in this animal preparation. The disappearance of [3H]progesterone from blood was described by two half-lives of 0·5 and 11·7 min. The metabolic clearance rate for this steroid was 2·9 litre/day, equivalent to a production rate of 3·9 μmol/day. The initial volume of distribution of the injected [3H]progesterone was 5·0 ml, a volume similar in size to the expected plasma volume. The total volume of distribution of [3H]progesterone (i.e. 'inner' and 'outer' pools) was in the range 24·8–35·4 ml.

The disappearance of endogenous progesterone from the blood of pseudopregnant rats after vascular isolation of the ovaries showed two half-lives of 1·1 and 11·4 min respectively. The disappearance of a product of reductive metabolism of progesterone, 20α-dihydroprogesterone, was apparently uniphasic, with a half-life of 41·3 min.
IMPORTANCE OF PERINATAL TESTOSTERONE IN SEXUAL DIFFERENTIATION IN THE MALE RAT
Authors: GOGAN F. , SLAMA A. , BIZZINI-KOUTZNETZOVA B. , DRAY F. , KORDON C.
Published: December 2008

Testosterone secretion in the male rat was high during the late fetal and immediate postnatal periods. It then showed a rapid decrease 3 h after birth and remained low until puberty.

Male rats from mothers given daily injections of an antibody to testosterone during the week before delivery displayed an LH peak when they were adult, orchidectomized and implanted with oestradiol. However, the amplitude of the peak was far smaller than in female rats from the same mothers treated in the same manner.

Thus, the critical period during which testosterone triggers hypothalamic sexual differentiation is very close to birth, possibly starting at the end of the fetal period.
MESENCEPHALIC AREAS CONTROLLING PULSATILE OXYTOCIN RELEASE IN THE SUCKLED RAT
Authors: JUSS T. S. , WAKERLEY J. B.
Published: December 2008

Experiments were performed on anaesthetized lactating rats to investigate the effects of radiofrequency lesions of the mesencephalon on the milk-ejection reflex. In lesioned and control rats, intramammary pressure recordings were used to estimate oxytocin release (number and relative amplitude of the intermittent milk-ejection responses) during a 3-h suckling test with ten pups. Bilateral lesions (diameter 0·5–1·5 mm) of the lateral tegmentum (near the brachium of the inferior colliculus and medial geniculate body) seriously disrupted the milk-ejection reflex, reducing the number of rats ejecting milk (two out of ten v. all 12 controls, P<0·001) and the amount of oxytocin they released (1·35±0·35 (s.e.m.) v. 15·52±2·19 mu. for controls, P<0·05). Unilateral lesions of the lateral tegmentum also impaired milk ejection and, if the suckling stimulus was restricted only to the contralateral nipples, oxytocin release was virtually abolished. Bilateral lesions placed more medially in the intermediate tegmentum were far less disruptive (eight out of nine rats ejected milk), though the amount of oxytocin released in this group (8·64±1·88 mu.) was still significantly (P<0·05) lower than controls. All rats with lesions of the central grey (nine) or ventral tegmentum (eight) displayed reflex milk ejection, as did those with multiple lesions of the tectum, central grey and ventral tegmentum (seven); in these three groups the amounts of oxytocin released (13·88±2·68, 13·10±1·90 and 11·04±1·95 mu. respectively) did not differ significantly from controls. Damage to the ventral tegmentum produced an irregular pattern of milk ejection characterized by occasional abnormally short (<2 min) milk-ejection intervals, though the overall number of responses in 3 h was less than that of controls (20·83±1·82 v. 14·50±1·30 mu., P<0·05). In conclusion, these results delineate two mesencephalic areas of particular importance in the milk-ejection reflex: (a) the lateral tegmentum, which appears to be concerned with transmission of the suckling stimulus from the contralateral nipples and is indispensable for oxytocin release, and (b) the ventral tegmentum which, although not an essential component of the reflex, may contribute to the timing of the intermittent milk-ejection responses.
LONG-TERM EFFECTS OF LEUCINE AND ARGININE ON B-CELL FUNCTION OF CULTIVATED PANCREATIC RAT ISLETS
Authors: SCHÄFER G. , SCHATZ H.
Published: December 2008

Leucine and arginine are well-known stimulators of insulin release, but they exert different actions on insulin biosynthesis in short-term incubations of isolated islets. In order to study their long-term effects on the B-cell, isolated rat islets were cultivated for 40 h in medium containing 0·5 or 3 mg glucose/ml supplemented with l-leucine (10 mmol/l) or l-arginine (10 mmol/l). After the culture the islets were incubated for 3 h with 2 mg glucose/ml without addition of the respective amino acid. Insulin biosynthesis was estimated from incorporation of [3H]phenylalanine or [3H]leucine into the (pro)insulin fraction of the islet proteins during this incubation.

At the low concentration of glucose, the leucine-cultivated islets released much more insulin than the control islets during culture as well as during subsequent incubation. At both glucose concentrations cultivation together with this amino acid resulted in an enhanced insulin biosynthesis.

The insulin-releasing effect of arginine with 0·5 mg glucose/ml was not as marked as that observed with an equimolar concentration of leucine. Islets cultivated with arginine showed no response to glucose during the incubation after culture. Hormone synthesis was found to be inhibited. Shortening of culture time to 20 h, followed by an additional 4 h of cultivation without arginine did not result in an improvement of B-cell function after culture.

It is concluded that leucine, in contrast with arginine, supports B-cell function, especially insulin biosynthesis, during long-term culture of islets. Stimulation of release of insulin with a concomitant inhibition of insulin biosynthesis caused by arginine during culture did not lead to a compensatory increase in hormone synthesis after culture.
EFFECTS OF TRIMETHOPRIM AND SULPHONAMIDE PREPARATIONS ON THE PITUITARY–THYROID AXIS OF RODENTS
Authors: COHEN H. N. , FYFFE J. A. , RATCLIFFE W. A. , McNICOL A. M. , McINTYRE H. , KENNEDY J. S. , THOMSON J. A.
Published: December 2008

The effects on pituitary–thyroid function of the commonly prescribed anti-bacterial preparations co-trimoxazole and co-trifamole, and their component drugs, have been studied in the rat and compared to the changes caused by propylthiouracil.

Co-trimoxazole and co-trifamole, in doses 20-fold in excess of a pharmacological dose administered for 10 days, produced marked changes in hormone levels consistent with blocking of thyroidal activity. Significant increases in thyroid gland weight, with histological evidence of hyperplastic goitre formation, were also demonstrated. Propylthiouracil produced less marked changes of thyroid hormone levels but higher levels of thyroid-stimulating hormone. Pharmacological doses of co-trimoxazole and co-trifamole and sulphamoxole, the sulphonamide component of co-trifamole, caused significant changes in thyroid hormone levels consistent with anti-thyroidal activity. In contrast, there was no evidence that trimethoprim, which is common to both preparations, or sulphamethoxazole, the sulphonamide component of co-trimoxazole, had an anti-thyroidal action, indeed, serum thyroxine levels were significantly increased at pharmacological dosage. We have concluded that the new commonly prescribed combination preparations retain the goitrogenic properties of the earlier sulphonamides.
RISE IN PLASMA CONCENTRATION OF ALDOSTERONE DURING LONG-TERM ANGIOTENSIN II SUPPRESSION
Authors: STAESSEN J. , LIJNEN P. , FAGARD R. , VERSCHUEREN L. J. , AMERY A.
Published: December 2008

The plasma concentration of aldosterone was followed in seven hypertensive patients before and during long-term angiotensin II suppression with the orally active angiotensin-I-converting-enzyme inhibitor, captopril. The plasma concentration of aldosterone decreased initially from 74 to 21 pg/ml (P < 0·05) after 1 month of administration of captopril. Thereafter the plasma concentration of aldosterone began to rise and after 1 year reached a level of 165 pg/ml. During long-term captopril therapy the plasma renin activity remained increased and the plasma angiotensin II concentration suppressed. The mechanism responsible for the late rise of the plasma concentration of aldosterone during long-term angiotensin II suppression with captopril remains to be elucidated. A sizeable and lasting hypotensive effect was observed in all patients.
AGE- AND MENTAL HEALTH-RELATED CIRCADIAN RHYTHMS OF PLASMA LEVELS OF MELATONIN, PROLACTIN, LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE IN MAN
Authors: TOUITOU YVAN , FÈVRE MICHÈLE , LAGOGUEY MICHEL , CARAYON ALAIN , BOGDAN ANDRÉ , REINBERG ALAIN , BECK HERVÉ , CESSELIN FRANÇOIS , TOUITOU CATHERINE
Published: December 2008

Circadian changes in plasma levels of melatonin, prolactin, LH and FSH were studied in four groups: seven healthy young men, six elderly men, six elderly women and six elderly demented patients (two men and four women). The daily activities of the subjects were synchronous and blood samples were taken every 4 h.

The 24-h mean concentrations of prolactin in plasma were the same in all groups, whereas those of LH and FSH were twice as high in the elderly as in the young men and eight and 23 times higher respectively in the elderly women. The 24-h mean plasma levels of melatonin in the elderly were half those in the young, but were not influenced by the sex or mental condition of the subjects.

A statistically significant circadian rhythm for melatonin was defined in the four groups, for prolactin in all groups except the elderly men and for LH only in the demented patients and in the young men. No circadian rhythm could be detected for FSH in any of the four groups. The acrophases of melatonin and prolactin ranged between 02.30 and 04.00 h, those of LH (when a rhythm was validated) clustered around 01.00 h.

The circadian rhythms of plasma levels of melatonin, prolactin and LH are not modified in old age nor in dementia. A positive correlation has been demonstrated in young men between melatonin and LH and between melatonin and prolactin, but no such correlation could be found in the elderly.
EFFECTS OF IN-VIVO ADMINISTRATION OF SEX HORMONES ON LUTEINIZING HORMONE-STIMULATED STEROID ACCUMULATION BY ISOLATED RABBIT OVARIAN FOLLICLES
Authors: YOUNGLAI E. V.
Published: December 2008

The effects of in-vivo administration of progesterone, testosterone propionate (TP) and oestradiol benzoate (OB) on steroid accumulation by isolated rabbit ovarian follicles were examined. Progesterone administration led to a suppression of follicular androgen accumulation when compared to controls injected with sesame oil. Follicles from these rabbits, when stimulated with LH, produced significant amounts of androgens. Administration of TP resulted in an increase in peripheral serum concentrations of progestins and a decrease in serum oestrogens. The follicles obtained after this treatment accumulated significantly less androgen and oestrogen than those from oil-injected rabbits. The response to LH by these follicles was similar to that of follicles from oil-treated rabbits in that significant increases were observed in progestin and androgen accumulation. Follicles from rabbits treated with OB accumulated more progestins and oestrogens than those from oil-treated animals. It is concluded that the hormonal environment of follicles can have profound effects on the subsequent response of follicles to further stimulation and activity, and that steroid treatment can influence the subsequent formation of that particular steroid.
EFFECTS OF HYPOTHYROIDISM ON THE BROWN ADIPOSE TISSUE OF ADULT RATS: COMPARISON WITH THE EFFECTS OF ADAPTATION TO COLD
Authors: MORY GERARD , RICQUIER DANIEL , PESQUIÉS PIERRE , HÉMON PHILIPPE
Published: December 2008

Hypothyroidism was induced in adult rats by oral absorption of methimazole and its effects on brown adipose tissue (BAT) were studied. Hypothyroidism partially mimicked the effects of chronic exposure to cold: BAT weight and its DNA content were increased and the mitochondrial components (proteins, phospholipids) of the tissue were greatly enhanced when expressed per unit of fresh tissue weight. Moreover, hypothyroidism had the same effects as adaptation to cold on the fatty-acid composition of both total and mitochondrial phospholipids. Basal respiratory rate and total cytochrome C oxidase activity of the tissue were also increased. However, the increase in the concentration of the '32 000 mol. wt protein', a polypeptide which regulates the dissipation of heat by BAT, was smaller and non-selective in hypothyroid rats. The amount of this protein was increased per mg tissue, but not per mg mitochondrial proteins, as in rats adapted to cold. Furthermore, in contrast with the large mobilization of the lipid stores in BAT of euthyroid animals, the BAT lipid stores of hypothyroid rats were not mobilized during the first hours of exposure to cold. It may be concluded that (a) hypothyroidism induces several alterations in BAT which are characteristic of an active thermogenic state (this may be because of the response of the organism to the deficiency of thermogenesis induced by hypothyroidism), (b) this potential increase in thermogenic capacity in the BAT of hypothyroid rats has probably a limited physiological role, since thyroid hormones are necessary for the mobilization of the tissue lipids which are the fuel for production of heat and (c) these data provide evidence for a limited role of thyroid hormones in the trophic response of BAT during adaptation to cold.
INSULIN RELEASE FROM THE PERFUSED RAT PANCREAS, STIMULATED BY PERIFUSATES OF THE PITUITARY NEUROINTERMEDIATE LOBES OF GENETICALLY OBESE AND LEAN MICE
Authors: DUNMORE SIMON , BELOFF-CHAIN ANNE
Published: December 2008

The perfused rat pancreas has been used to study the dynamics of insulin release during stimulation with a perifusate of the pituitary neurointermediate lobe (NIP) of genetically obese mice (ob/ob) and their lean litter-mates (+/+). It has been shown that the NIP of ob/ob mice is more active. The remainder of the study was carried out with NIP from ob/ob mice. The results showed that both phases of insulin release stimulated by 16·6 mm-glucose were increased by NIP. When the pancreas was first stimulated with NIP in the presence of 5·5 mm-glucose, followed by a high concentration of glucose, it responded to the latter with a normal biphasic response. If, however, the pancreas was stimulated first with glucose the response to NIP was refractory.

The results are discussed in relation to the possible significance of an insulin secretagogue from the pituitary pars intermedia in the hyperinsulinaemia associated with obesity.
EFFECT OF SODIUM MOLYBDATE ON THE INTERACTION OF ANDROGENS AND PROGESTINS WITH BINDING PROTEINS IN HUMAN HYPERPLASTIC PROSTATIC TISSUE
Authors: SIRETT D. A. N. , GRANT J. K.
Published: December 2008

A reliable measurement of steroid hormone receptors is essential for attempts to correlate receptor levels with response to endocrine therapy in prostatic carcinoma. Evidence that receptors in many tissues are stabilized by sodium molybdate prompted the examination of the effects of this salt on the measurement of steroid-binding sites in human prostatic tissue. The presence of molybdate (10 mmol/l) during tissue homogenization, cytosol or nuclear extract preparation and binding-site assay led to a threefold increase in the amount of highaffinity androgen binding detected in cytosol, and a slight increase in the number of cytosol progestin-binding sites. The apparent binding affinity for steroids was increased in both cases. No effect of molybdate was observed on androgen-binding sites in nuclear extracts.
EFFECTS OF PROGESTERONE, OESTRADIOL-17 β AND ANDROSTENEDIONE ON FOLLICULAR GROWTH AFTER REMOVAL OF THE CORPUS LUTEUM DURING LACTATIONAL AND SEASONAL QUIESCENCE IN THE TAMMAR WALLABY
Authors: RENFREE M. B. , WALLACE G. I. , YOUNG I. R.
Published: December 2008

The corpus luteum was removed from tammar wallabies during either lactational or seasonal quiescence, and the pouch young were replaced on the teat after lutectomy. Follicular development resumed and the animals came into oestrus 11–14 days later. Injections of oil, progesterone or androstenedione did not prevent follicular growth, although ovulation only occurred in one animal, but treatment with oestradiol-17β, either alone or mixed with progesterone, inhibited the development of follicles. These results suggest that oestrogen, of luteal origin, is responsible for the suppression of follicular development during lactational and seasonal quiescence.
NORMAL FUNCTION OF EXTRA-ADRENAL CHROMAFFIN TISSUES IN THE YOUNG RABBIT AND GUINEA-PIG
Authors: COUPLAND R. E. , KENT CHRISTINE , KENT S. E.
Published: December 2008

An attempt has been made to determine the relative functional activities of adrenal and extra-adrenal chromaffin tissue during the neonatal phase and up to 1 week of age using young rabbits and guinea-pigs whose main extra-adrenal abdominal para-aortic chromaffin bodies are respectively non-innervated and innervated.

Amine synthesis and storage were followed by assay and autoradiography after a single intraperitoneal injection of l-[2,5,6-3H]DOPA and the findings correlated with amine content as assessed by high performance liquid chromatography and by volume of tissue.

The results indicate that in the guinea-pig, in spite of differences in proportions of adrenaline and noradrenaline in the adrenal gland and para-aortic body (PAB), the loss of labelled catecholamines from the innervated PAB closely follows that from the adrenal medulla, suggesting that both participate in normal sympathoadrenal activity. By comparison, in the rabbit the PAB shows only a minimal decrease in labelled amine during the first week of life during which period the amine content and concentration of the PAB doubles: the functional significance of this non-innervated extra-adrenal chromaffin tissue, which persists throughout life, has still to be determined.
Androgen and oestrogen concentrations in the ovary of the cyclic rat
Authors: Toorop A. I. , Gribling-Hegge L.
Published: December 2008

In the 5-day cyclic rat the ovarian androgen and oestrogen concentrations, measured by radioimmunoassay, started a gradual rise on the day of metoestrus, reaching maximal values in the period from 22.00 h on dioestrus 2 until 17.00 h on the day of pro-oestrus. A steep decline in the ovarian androgen and oestrogen concentrations occurred between 17.00 and 21.00 h on the day of pro-oestrus.

Rats, injected intraperitoneally with an ovulation-blocking dose of pentobarbitone sodium (35 mg/kg body weight) at 13.00 h on the day of pro-oestrus, tended to show a decline in ovarian concentrations of androgens and oestrogens during late pro-oestrus, but this decrease was less steep than in saline-injected rats. At 10.00 and 14.00 h on the day after pro-oestrus the ovarian concentrations of androgens and oestrogens in rats treated with pentobarbitone sodium showed a further decline but values were still higher than those in saline-treated oestrous rats. At 17.00 h, i.e. 28 h after injection with pentobarbitone sodium, a distinct increase in the ovarian androgen and oestrogen concentrations was noted and a steep decline was observed at 21.00 h on the day after pro-oestrus.

Thus normal as well as delayed ovulation was preceded first by an increase and then by a steep decline in ovarian concentrations of oestrogens and androgens.
Fetal growth inhibition and decreased thyroid activity after injection of oestradiol benzoate into pregnant rats
Authors: Kühn E. R. , Bollen M. , Darras V.
Published: December 2008

Pregnant rats were subcutaneously injected daily with 10 μg oestradiol benzoate (OB) and/or 1 mg bromocriptine starting on day 15 of gestation. After treatment with OB, but not bromocriptine, lower fetal body weight, fetal length and placental weight were observed. The administration of bromocriptine did not influence maternal plasma levels of prolactin, but fetal levels were decreased on day 22 of gestation. Oestradiol benzoate raised prolactin concentrations in maternal plasma on days 20 and 22, whereas fetal plasma levels were raised on day 22. This increase was counteracted by simultaneous administration of bromocriptine and OB, whereas impairment of fetal growth remained after treatment. A slight decline in fetal plasma levels of insulin was observed once, but thyroid content of triiodothyronine and thyroxine (T4) was decreased to a quarter and a third respectively of control levels in male and female fetuses of OB-treated rats, fetal circulating levels of T4 were also depressed. Maternal and fetal plasma glucose levels were decreased. A close correlation between T4 and placental or fetal weight was always present on day 22 of gestation. It was concluded that OB injected into pregnant rats will reach the fetal circulation as judged by increases in fetal plasma levels of prolactin. The observed fetal growth retardation after the OB injection was associated with thyroid deficiency, whereas plasma levels of prolactin and insulin were either not at all or only slightly altered. A direct effect of OB on placental blood flow and hence on the fetal food supply cannot, however, be excluded.
Uptake of 125I-labelled prolactin by bullfrog kidney tubules: an autoradiographic study
Authors: Gona Ophelia
Published: December 2008

The uptake of 125I-labelled ovine prolactin in the bullfrog kidney was studied by autoradiography. Five minutes after the intracardiac injection of 125I-labelled prolactin, no labelling was detected in the kidneys of premetamorphic tadpoles or in animals whose forelimbs had just emerged (climax tadpoles). After 15 min, a few isolated tubules were labelled in the premetamorphic tadpole kidneys and many kidney tubules were labelled in climax tadpoles. In the froglet kidneys, extensive labelling was seen by 5 min after injection, and only distal tubules seemed to be consistently unlabelled. The radioactive label was displaced by an excess of unlabelled ovine prolactin, but not by ovine growth hormone or bovine LH. These findings provide the first morphological demonstration of specific binding of prolactin by the nephric tubules of an amphibian. They show that the receptors, present in small numbers in the premetamorphic stage, proliferate during the later stages of metamorphosis. The change in receptor density involves both an increase in the number of tubules having receptors and in the density of receptors per tubule.
Distribution of 125I-labelled follicle-stimulating hormone and human chorionic gonadotrophin in the gonads of hypogonadal (hpg) mice
Authors: Charlton H. M. , Parry Dilys , Halpin D. M. G. , Webb R.
Published: December 2008

Hypogonadal mice are deficient in LH releasing hormone (LH-RH), the releasing factor for LH and FSH, with a consequent failure of postnatal ovarian and testicular development. After intravenous injection of hypogonadal females with 125I-labelled human chorionic gonadotrophin (hCG), followed by autoradiography of semi-thin (1 μm) slices of the ovary, labelled hCG was found to be associated with interstitial cells and thecal cells with little or no labelling of granulosa cells. Labelled human FSH was associated solely with granulosa cells. Hypogonadal females, implanted for 5 days with a silicone elastomer capsule of oestrogen, showed a similar response to that of normal females with hCG labelling of the granulosa cells of the larger follicles as well as of the thecal cell layer. Furthermore, subcutaneous injection of hypogonadal females with LH-RH (50 ng), 12 times daily for 5 days, increased uterine weight and stimulated ovarian development with some large follicles binding hCG to both thecal and granulosa cells. Therefore stimulation of follicular development may possibly be associated with increased oestradiol concentrations.

In the male, after injection of 125I-labelled hCG, silver grains were associated with the interstitial cells alone in both hypogonadal and normal mice. Labelled human FSH was undetectable in semi-thin testicular sections, but the mode of injection (intravenous) may not have allowed enough labelled hormone to reach the testis in order to resolve the question as to whether the hypogonadal or normal testis can bind FSH.
In-vivo uptake and metabolism of testosterone by the skin and other tissues of the rat
Authors: Randall Valerie A. , Ebling F. J. , Hargreaves G.
Published: December 2008

The uptake and metabolism of radioactively labelled testosterone was investigated in vivo at various time intervals in the skin, plasma and other tissues of adult rats castrated 24 h earlier. After the addition of marker steroids the components of the tissue extracts were separated by partition and development in several chromatographic systems; steroid identification was confirmed by derivative formation and recrystallization to constant 3H:14C ratio.

The skin resembled the classical androgen target organs in the uptake and retention of both total and unconjugated radioactivity, but the actual composition of the radioactivity present in the skin was markedly different from that in the accessory glands. Little testosterone was recovered from the ventral prostates and 5α-dihydrotestosterone (5α-DHT), often considered the active intracellular androgenic steroid, constantly occupied the largest proportion of the extracted radioactivity. In the skin samples, however, testosterone was always the major unconjugated steroid detected and 4-androstene-3,17-dione, 5α-DHT, 5α-androstane-3α,17β-diol, androsterone and 5α-androstane-3β,17β-diol were only identified in much smaller quantities, even after 5 h. Although the majority of the plasma radioactivity was conjugated or very polar by 20 min, all the steroids found in the skin were present, albeit in different proportions; testosterone was always predominant and 5α-androstane-3β,17β-diol was also detected in larger amounts than the very low levels of the other steroids.

The results suggest that 5α-DHT is not as important in the skin as it is in the prostate of the rat and that other androgenic steroids, most notably testosterone itself, may be involved in the mechanism of androgen action in the skin.
Serum concentrations of testosterone throughout pregnancy in rats
Authors: Bridges R. S. , Todd R. B. , Logue C. M.
Published: December 2008

Testosterone concentrations in serum of rats bled throughout pregnancy and post partum were measured using Celite microcolumn chromatography and a radioimmunoassay for testosterone. Mean serum levels of testosterone ranged from about 170 to 340 pmol/l during the first 10 days of pregnancy. Significant increases in concentrations of testosterone in serum of pregnant rats were found on days 12, 15 and 18 of gestation. The highest testosterone concentrations occurred on days 18 and 20 of pregnancy when mean levels were 3228 and 3685 pmol/l respectively. Testosterone levels declined before parturition on day 22 (mean = 1449 pmol/l and declined further after parturition (mean = 315 pmol/l). In order to determine whether serum testosterone concentrations varied during the day in the pregnant rat, samples were collected at 6-h intervals on days 6–7 and 14–15 of gestation. Diurnal variations in serum testosterone concentrations were not evident during early or late pregnancy, unlike the rhythmic changes in serum prolactin levels found at these times during early pregnancy. The possible sources of the increased titres of serum testosterone during the second part of gestation in rats are discussed.
An assay of the capacity of biological fluids to stimulate renal glucose-6-phosphate dehydrogenase activity in vitro as a marker of their ability to inhibit sodium potassium-dependent adenosine triphosphatase activity
Authors: Fenton S. , Clarkson E. , MacGregor G. , Alaghband-Zadeh J. , de Wardener H. E.
Published: December 2008

A highly sensitive cytochemical method for the assay of the ability of plasma and extracts of human urine to stimulate renal glucose-6-phosphate dehydrogenase (G6PD) activity in vitro is described. In the proximal convoluted tubules there was a linear increase of G6PD activity with the logarithm of concentration of a highly purified natriuretic extract from normal human urine (0·384–384 ng active material/l) which was used as a standard. The stimulation of G6PD obtained with dilutions of normal human plasma was parallel to that produced by the standard. The sensitivity of the assay permitted the measurement of as little as 0·384 ng active material/l of the natriuretic extract (0·001 units/ml) and dilutions of 1/10 000 could be detected using normal human plasma. The mean ± s.e.m. index of precision was 0·068± 0·003 (n = 9).

It is known that inhibition of sodium potassium-dependent adenosine triphosphatase (Na+-K+-ATPase) is associated with a rise in G6PD activity. We have confirmed this observation by demonstrating that ouabain, a potent inhibitor of Na+ -K+-ATPase, stimulates renal G6PD activity in our assay and that natriuretic extract, human plasma and ouabain stimulated renal G6PD activity in vitro and simultaneously inhibited renal Na+-K+-ATPase activity in vitro.

The plasma from 12 normal subjects (five of whom were previously shown to inhibit renal Na+-K+-ATPase activity in vitro in a manner related to sodium intake) stimulated renal G6PD activity in vitro, and this activity was also directly related to sodium intake.

It is suggested that the change in the capacity of plasma to stimulate renal G6PD activity in vitro is a marker of the concentration of a circulating sodium transport inhibitor.
Effect of composition of incubation medium on aldosterone and corticosterone production by isolated rat zona glomerulosa cells
Authors: Campbell D. J.
Published: December 2008

The role of the composition of the incubation medium in determining the steroidogenic responsiveness of collagenase-dispersed rat zona glomerulosa cells was examined by studying the effect on production of aldosterone and corticosterone of (1) changes in the bovine serum albumin (BSA) concentration in Krebs–Ringer bicarbonate buffer (KRBGA), (2) dialysis of the BSA and (3) comparison of KRBGA with 'modified' Medium 199. Medium 199 was modified so that its electrolytic content was identical to that of KRBGA.

Compared with 0·1–0·2% BSA in KRBGA, BSA concentrations of 0·5 and 4% caused inhibition of both basal and K+-stimulated, but not angiotensin II-stimulated steroidogenesis. This inhibitory property of BSA was not removed by dialysis. The BSA did, however, contain a dialysable factor which increased both basal steroidogenesis and the steroidogenic response to maximal K+ and angiotensin II stimulation.

Both incubation media contained 0·2% BSA for the comparison of KRBGA with modified Medium 199. Modified Medium 199 increased both basal steroidogenesis and the aldosterone response to K+ stimulation (per cent increase above basal) by two- to threefold compared with KRBGA, with smaller increases in the response to ACTH and 5-hydroxytryptamine (5-HT) and a decrease in the response to cyclic AMP. In contrast, modified Medium 199 increased the aldosterone response to angiotensin II by sevenfold, from 60% (in KRBGA) to 420%.

In KRBGA, angiotensin II inhibited K+-stimulated aldosterone production. This effect was produced by concentrations of angiotensin II below the threshold for steroidogenesis and could be reproduced with the angiotensin II antagonist [Sar1, Ileu8]-angiotensin II. Angiotensin II did not inhibit K+-stimulated aldosterone production in modified Medium 199.

These data emphasize the importance of the composition of the incubation medium in determining the steroidogenic responsiveness of rat zona glomerulosa cells in vitro. Furthermore, these data indicate that the steroidogenic response to angiotensin II, compared with K+, ACTH, 5-HT and cyclic AMP, is more readily influenced by other, as yet unidentified, factors in the incubation medium, and are consistent with recent evidence that angiotensin II and K+ do not share a common mode of action on steroidogenesis by these cells.
Cyclic GMP concentration in ovarian tissue after administration of gonadotrophin to prepubertal rats
Authors: Major Patricia W. , Cunningham Janette
Published: December 2008

The weights, protein concentrations, and concentrations of cyclic AMP and cyclic GMP in the ovaries of prepubertal rats have been measured after induction of follicular growth by administration of pregnant mare serum gonadotrophin (PMSG). Three phases of ovarian growth, the follicular growth phase, the preovulatory phase and the luteal phase were investigated. Ovulation was induced by administration of human chorionic gonadotrophin (hCG). During the follicular phase, ovarian weight, protein content and the content of both cyclic AMP and cyclic GMP increased 2–3 days after administration of PMSG. Administration of hCG 65 h after PMSG caused a rapid rise in the concentration of cyclic AMP but the concentration of cyclic GMP tended to fall. During the luteal phase the concentrations of both cyclic nucleotides decreased.
Role of prolactin in vitamin D metabolism and calcium absorption during lactation in the rat
Authors: Robinson C. J. , Spanos E. , James M. F. , Pike J. W. , Haussler M. R. , Makeen A. M. , Hillyard C. J. , MacIntyre I.
Published: December 2008

Intestinal calcium absorption and plasma levels of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) were measured in lactating and non-lactating rats and the effects of bromocriptine and exogenous prolactin treatment were evaluated. In lactating rats calcium absorption and plasma levels of parathyroid hormone, 1,25(OH)2D3 and alkaline phosphatase activity were significantly increased. Bromocriptine treatment significantly reduced the enhanced calcium absorption and levels of plasma 1,25(OH)2D3 and alkaline phosphatase but had no significant effect on plasma levels of parathyroid hormone. Prolactin administered with bromocriptine to lactating animals prevented all the changes observed with bromocriptine treatment alone. It was concluded that the increased plasma levels of prolactin during lactation lead to high plasma levels of 1,25(OH)2D3 which are responsible for the enhanced intestinal calcium absorption.
Effects of 2-hydroxyoestradiol-17β on plasma luteinizing hormone, follicle-stimulating hormone and prolactin, and nuclear translocation of pituitary oestrogen receptors in ovariectomized ewes
Authors: Clarke I. J. , Wynne K. , Funder J. W. , Findlay J. K.
Published: December 2008

The ability of oestradiol-17β (OE2) and 2-hydroxyoestradiol (2OH-OE2) to translocate pituitary oestrogen receptors to the nuclear compartment and to affect plasma concentrations of LH, FSH and prolactin was studied in ovariectomized ewes. Mean (± s.e.m.) nuclear oestrogen receptor levels (% of total pituitary oestrogen receptors) after intracarotid injections of 1·25 μg OE2, 400 μg 2OH-OE2 or vehicle were 8·7±2·3, 16·9 ± 3·2 and 0·8±0·1% respectively. Whereas 1·25 or 12·5 μg OE2 significantly lowered plasma LH and FSH, 400 μg 2OH-OE2 did not affect plasma LH or FSH levels. Injection of 4000 μg 2OH-OE2, however, significantly affected plasma LH and FSH. Plasma prolactin levels were not significantly affected by the treatments. These data indicate a discrepancy between oestrogen receptor occupancy and effects on gonadotrophin and prolactin secretion after injection of catechol oestrogen.
Inter-species comparison of somatomedin structure using immunological probes
Authors: Wilson D. M. , Hintz R. L.
Published: December 2008

To explore the structural differences in various animal somatomedins, we examined the sera of 20 animal species using two region-specific radioimmunoassays, a radioimmunoassay specific for somatomedin-C and a placental membrane radioreceptor assay. Using small peptide portions of the insulin-like growth factor-I (IGF-I) C chain and D chain made by solid-state methods, we generated antisera in rabbits and developed radioimmunoassays to these regions. For a radioimmunoassay directed against intact somatomedin-C, we used the antibody distributed by the NIH (NIH-radioimmunoassay). For the detection of somatomedin peptide content, we used a placental membrane radioreceptor assay. 125I-Labelled IGF-I was used as the radioligand in all assays and an insulin-free, partially purified somatomedin preparation was used for the standard curves. All samples were chromatographed in 0·25 m-formic acid to remove any somatomedin-binding protein before assay.

The correlation between the radioreceptor assay and the NIH-radioimmunoassay was good (r2 = 0·84) but the slope was significantly (P<0·001) different from a value of 1 which would be expected if the two assays were detecting equal amounts of somatomedin activity. In all the species, the somatomedin level measured by radioreceptor assay was greater than that measured by the NIH-radioimmunoassay, suggesting the presence of a somatomedin-like protein which has retained its ability to bind to the somatomedin receptor but which is sufficiently different to give it reduced affinity in the NIH-radioimmunoassay.

The somatomedins of rat, hamster and mouse (all rodents of the superfamily Myomorpha) were not detectable using the radioimmunoassays for the C and D chains of IGF-I, although they were high in the radioreceptor assay. This suggests that these regions have a different structure from the analogous regions in the guinea-pig (a rodent of the superfamily Caviomorpha) and implies a significant structural change in a somatomedin-like molecule during the evolution of the order Rodentia. This is analogous to the marked differences in the known sequence of the pro-insulins in these two superfamilies.
The International Reference Preparation of Gonadorelin for Bioassay: a comparison with different preparations of synthetic luteinizing hormone releasing hormone using physicochemical methods of analysis, different bioassays and immunoassay
Authors: Storring P. L. , Corran P. H. , Gaines Das Rose E. , Calam D. H.
Published: December 2008

The preparation and nature of the International Reference Preparation of Gonadorelin for Bioassay (IRP; coded 77/596) are described.

The IRP was studied by four laboratories in four countries and compared, using physicochemical methods of analysis, various bioassay procedures and immunoassay, with preparations of synthetic luteinizing hormone releasing hormone (LH-RH) produced by different manufacturers.

Analyses by thin-layer chromatography and by reverse-phase high-performance liquid chromatography (HPLC) indicated some heterogeneity of the peptide present in most of these preparations of synthetic LH-RH, including that of the IRP; the latter preparation appeared to be 88·3% (w/w) pure, judged by HPLC. The data from the collaborative study suggested that each ampoule of the IRP contains approximately 31 nmol LH-RH.

The IRP appeared to be suitable to serve as an international reference preparation for bioassay since its behaviour was similar in different bioassays, so far as this could be examined, to that of the other preparations of LH-RH with which it was compared. Furthermore, the biological activities of different preparations of LH-RH, assessed in terms of the IRP, appeared to correlate with their degrees of purity assessed by physicochemical methods, suggesting that the peptides other than LH-RH present in the IRP did not contribute significantly to the biological activity of the preparation in these assay procedures. The limited data available suggested that the IRP might also be suitable as a reference preparation for immunoassay.

The ampouled preparation, coded 77/596, was therefore established by the World Health Organization as the International Reference Preparation of Gonadorelin for Bioassay and assigned a unitage of 31 i.u./ampoule on the basis that the i.u. is represented by 1 nmole of LH-RH.