bluuebunny/crossref_metadata_2025 huggingface dataset:
Sexual maturation of male rats treated postnatally with a gonadotrophin-releasing hormone antagonist
Authors: Kolho K.-L. , Nikula H. , Huhtaniemi I.
Published: December 2008

Postnatal secretion of gonadotrophin by male rats was inhibited by a potent gonadotrophin-releasing hormone (GnRH) antagonist analogue (N-Ac-4-Cl-d-Phe1,4-Cl-d-Phe2,d-Trp3,d-Phe6,des-Gly10-GnRH-d-alanylamide; Org 30039; 2 mg/kg s.c. twice daily) on days 1–5, 6–10, 11–15 or 16–20 of life. The onset of puberty was determined by monitoring the separation of the preputium from the glans penis, i.e. balanopreputial separation (BPS). Rats treated on days 1–5 matured normally, whereas all treatments between days 6 and 20 delayed BPS (P < 0·01). In adult rats (between 110 and 160 days of age), testis weights were reduced by 21–35% (P < 0·01) in groups treated between days 1 and 15, although weights of the accessory sex glands were normal. Testicular FSH receptors were decreased by 31–47% (P < 0·01) in all treatment groups, whereas the LH receptor content was decreased only in rats treated between days 1 and 5 (18%; P < 0·05) and prolactin receptor content decreased only in rats treated up to day 10 (31–33%; P < 0·01). Concentrations of serum testosterone, LH and FSH, and pituitary contents of LH and FSH were unaffected by neonatal treatment with Org 30039. Animals treated with Org 30039 had reduced fertility which was most pronounced (88%; P < 0·01) in rats treated between days 1 and 5. However, motile sperm were detectable in the cauda epididymis of the infertile rats.

In conclusion, postnatal gonadotrophin deprivation induced with a GnRH antagonist for different 5-day periods during the first 15 days of life delayed puberty, reduced adult testis weight and impaired fertility. Some effects of the antagonist were largely independent of the timing of gonadotrophin suppression. Other effects, including suppression of testicular LH and prolactin receptors and the delay in the onset of puberty, were found only in the younger and older treatment groups respectively. These findings emphasize the importance of neonatal hypothalamic-pituitary-gonadal function for subsequent sexual maturation.

J. Endocr. (1988) 116, 241–246
Comparison of peptide release from fetal rat hypothalamic neurones cultured in defined media and serum-containing media
Authors: Clarke M. J. O. , Gillies G. E.
Published: December 2008

Primary cultures of rat hypothalamic neurones were maintained either in a serum-supplemented medium or in a serum-free chemically defined medium for up to 6 weeks. The release of the 41 amino acid-containing peptide, corticotrophin-releasing factor (CRF-41), vasopressin (AVP) and somatostatin (SRIF) were followed using immunoassays. In response to K+ (56 mmol/l) depolarization both the quantities of peptides released and the magnitude of responses were significantly greater from cultures maintained in the fully supplemented defined medium. As a consequence, release of CRF-41 and AVP could be measured directly, without requiring the concentration step necessary for cultures grown in serum. The response to K+ depolarization increased with the age of the culture, suggesting neuronal maturation.

Responses to K+ depolarization were Ca2+-dependent, and the addition of corticosterone (100 nmol/l) to the defined medium caused a significant reduction in the response of neurones secreting CRF-41 and AVP, but not those secreting SRIF, to depolarization. This suggests the retention in vitro of the responsiveness of stress-associated neuropeptides to the negative feedback effects of corticosterone. Neurones producing CRF-41 and AVP responded significantly in a dose-dependent manner to acetylcholine stimulation, whereas those producing SRIF did not. As cultures matured, the CRF-41- and AVP-producing neurones became more sensitive to acetylcholine with the maximal response at 1 nmol acetylcholine/1.

In conclusion, the culture of rat hypothalamic neurones is improved in terms of peptide output when the cultures are maintained in a defined medium. Differential responses of the peptidergic neurones may be seen in the presence of corticosterone and neurotransmitters, illustrating the retention in vitro of specific receptor-mediated responses which have been observed in vivo. This model should prove useful in the further study of the physiological, pharmacological and biochemical maturation and control of peptidergic neurones.

J. Endocr. (1988) 116, 349–356
Thyroid and parathyroid-independent increase in plasma 1,25-dihydroxyvitamin D during late pregnancy in the rat
Authors: Nguyen T. M. , Halhali A. , Guillozo H. , Garabedian M. , Balsan S.
Published: December 2008

The effect of thyroparathyroidectomy (TPTX) on the plasma concentrations of the vitamin D metabolites (25-(OH)D, 24,25-(OH)2D and 1,25-(OH)2D) has been studied in pregnant rats and their fetuses during the last quarter of gestation.

Maternal and fetal vitamin D metabolites were not significantly affected by TPTX. A significant increase in plasma 1,25-(OH)2D concentrations was observed in both TPTX and control mothers and fetuses from days 19 to 21. Fetal and maternal plasma 25-(OH)D were positively correlated in both control and TPTX groups. Such a correlation was also found for 24,25-(OH)2D in the two groups. In contrast, a positive correlation between maternal and fetal plasma concentrations of 1,25-(OH)2D was found in TPTX but not in control rats.

These data suggest that major alterations in calcium metabolism, such as that produced by maternal TPTX, are insufficient to affect the changes in maternal and fetal plasma 1,25-(OH)2D during late pregnancy significantly. They also suggest that parathyroid hormone, thyroxine, and/or calcitonin may control a possible placental transfer of 1,25-(OH)2D in the rat.

J. Endocr. (1988) 116, 381–385
Effects of treatment of neonatal rats with highly purified FSH alone and in combination with LH on testicular function and endogenous hormone levels at various ages
Authors: Ultee-van Gessel A. M. , Timmerman M. A. , de Jong F. H.
Published: December 2008

Factors which play a role in the regulation of testicular size in rats were investigated using neonatal animals treated with exogenous gonadotrophins for 2 or 3 weeks, starting on the day after birth. Effects on testis weight and various aspects of the pituitary-testicular axis were evaluated up to the age of 9 weeks.

Daily treatment with human FSH (Metrodin; 0·15 U/g body wt) for 2 or 3 weeks, starting on the first day or 1 week after birth, resulted in enlargement of the testes, increased testicular content of inhibin and a suppression of pituitary and plasma FSH. The relative increase of testis weight decreased after cessation of treatment. Injections of human FSH combined with administration of human LH (Pergonal) for 3 weeks, starting on the first day after birth, resulted in larger testes immediately after treatment. In addition, an increased amount of interstitial tissue was observed in these animals. Pituitary and plasma FSH and LH were suppressed after this treatment, while the growth of the accessory sex organs was significantly stimulated.

In animals treated with human FSH during the first 2 or 3 weeks of life, levels of rat FSH in blood samples collected at weekly intervals were significantly suppressed until the animals were killed at the age of 9 weeks. In the animals treated with human FSH and human LH, both FSH and testosterone concentrations were significantly lower than those in control animals between the ages of 4 and 9 weeks. At the age of 9 weeks testicular weights were still higher than those in control animals after these treatments. In the treated animals, no histological abnormalities of spermatogenesis were observed.

We conclude that the first 3 weeks after birth are important for the establishment of testis size in the rat because during this period it is possible to stimulate mitoses of Sertoli cells with FSH. To obtain a permanent increase in testis size a longer period of treatment with exogenous gonadotrophins is needed. A possible feedback suppression of endogenous gonadotrophins by inhibin in FSH-treated rats and by inhibin and testosterone in the FSH- and LH-treated 3-week-old animals could be the reason for the relative delay of testicular development after the end of the treatments. The low endogenous level of LH which was observed caused impaired Leydig cell function in animals which were treated with FSH and LH.

J. Endocr. (1988) 116, 413–420
Radioimmunoassay of progesterone receptor in human tissues: application to breast cancer
Authors: Brailly S. , Lorenzo F. , Jolivet A. , Logeat F. , Pallud C. , Milgrom E.
Published: December 2008

A radioimmunoassay method to measure progesterone receptor in rabbit and human tissues was devised and applied to human breast cancer. A specific progesterone receptor antibody was prepared by purifying rabbit receptor by immunoaffinity chromatography, sodium dodecylsulphate-polyacrylamide gel electrophoresis and injection of the isolated 110 000 dalton receptor band into a goat. Immunoblot studies of progesterone target and non-target tissues showed the specificity of the antibody, which was used at a dilution of 1/45 000. The tracer consisted of 125I-labelled electroeluted 110 000 dalton receptor.

The sensitivity of the method was 1 fmol/tube for the rabbit receptor and 3 fmol/tube for the human receptor. The intra-assay coefficient of variation was 11% for tumours positive for the progesterone receptor and 9·9% for those on the borderline (10–30 fmol receptor/mg protein). The interassay coefficients of variation were 20 and 19% respectively. The correlation between the radioimmunoassay and a steroid-binding assay was studied in 40 tumour biopsies. In 39 cases, very good correlation was found (r = 0·99); in a single case an immunoreactive protein was detected which apparently bound steroid poorly.

One important feature of this method was that receptor immunoreactivity remained unchanged when either the tissue or the cytosol was exposed to a temperature of 20 °C for relatively long periods of time. Under the same conditions the steroid-binding capacity declined rapidly. This characteristic of the radioimmunoassay may prevent errors due to improper handling of tissue samples. Such stability was not observed for oestrogen receptors when measured by a sandwich immunoenzymatic method after incubation of tissue at 20 °C.

J. Endocr. (1988) 116, 427–434
Plasma LH and testosterone responses to gonadotrophin-releasing hormone in adult red deer (Cervus elaphus) stags during the annual antler cycle
Authors: Fennessy P. F. , Suttie J. M. , Crosbie S. F. , Corson I. D. , Elgar H. J. , Lapwood K. R.
Published: December 2008

Eight adult red deer stags were given an i.v. injection of synthetic gonadotrophin-releasing hormone (GnRH) on seven occasions at various stages of the antler cycle, namely hard antler in late winter, casting, mid-velvet growth, full velvet growth, antler cleaning and hard antler both during the rut and in mid-winter. The stags were allocated at random on each occasion to one of four doses, i.e. 1, 3, 10 or 95 μg GnRH. Blood samples were taken before GnRH injection and for up to 2 h after injection. Pituitary and testicular responses were recorded in terms of plasma LH and testosterone concentrations.

There was an increase in plasma concentration of LH after the GnRH injection in all stags at all stages of the antler cycle. Dose-dependent responses of LH to GnRH in terms of area under the curve were apparent at all stages of the antler cycle. The lowest responses were recorded at casting, during velvet antler growth and at the rut sampling.

The pattern of testosterone response reflected the inter-relationship of the antler and sexual cycles with very low testosterone responses occurring at casting and during velvet antler growth. The responses were higher at antler cleaning and then increased to a maximum at the rut before declining to reach their nadir at casting. The results are consistent with a hypothesis that the antler cycle, as a male secondary sexual characteristic, is closely linked to the sexual cycle and its timing is controlled by reproductive hormones. Low plasma concentrations of testosterone, even after LH stimulation, are consistent with the hypothesis that testosterone is unnecessary as an antler growth stimulant during growth.

J. Endocr. (1988) 117, 35–41
Monoclonal antibody enhancement of the effects of human growth hormone on growth and body composition in mice
Authors: Holder A. T. , Blows J. A. , Aston R. , Bates P. C.
Published: December 2008

Dwarf mice were treated for 10 days with phosphate-buffered saline (PBS), human growth hormone (hGH) or hGH with monoclonal antibody EB1 (hGH/MAB-EB1); for each treatment there were three groups which received 50, 75 or 100% of the amount of food eaten when available ad libitum.

The PBS control groups lost more or gained less weight than equivalent groups receiving hGH alone, and mice given hGH/MAB-EB1 showed a greater weight gain than those in comparable groups receiving hGH alone. When weight gain or loss was expressed as g/g food eaten, groups treated with hGH gained more or lost less than the PBS groups. Similarly, weight gain/g food was significantly greater in hGH/MAB-EB1 animals than in the comparable groups given hGH alone. A similar pattern of response was observed for increases in tail length and uptake of 35SO42− into costal cartilage in vivo. For mice given hGH alone, fat content was decreased compared with that in the equivalent group given PBS, and mice treated with hGH/MAB-EB1 had less fat than the equivalent group given hGH alone. Administration of hGH alone caused a concomitant increase in protein content and body weight such that, compared with mice given PBS, there was no significant increase in protein as a proportion of body weight. However, hGH/MAB-EB1 caused an increase in whole body protein which was significantly greater than that for the equivalent group given hGH alone, when expressed as per cent body weight.

Monoclonal antibody EB1 has been shown to enhance the actions of hGH on growth and body composition in Snell dwarf mice and to increase food conversion efficiency.

J. Endocr. (1988) 117,85–90
Differential secretion of pro-opiomelanocortin peptides by the pars distalis and pars intermedia of beagle dogs
Authors: Kemppainen R. J. , Sartin J. L.
Published: December 2008

Beagle dogs were given saline, insulin or the dopamine antagonist, haloperidol, to examine peripheral concentrations of immunoreactive (ir)-pro-opiomelanocortin (POMC) peptides resulting from pars distalis or pars intermedia stimulation. Six beagles were given each test substance on separate occasions with and without dexamethasone pretreatment. Plasma was assayed directly for glucose, ir-ACTH, ir-α-MSH, cortisol and, after Sephadex G-50 Fine gel filtration chromatography, for ir-β-lipotrophin (ir-β-LPH) and ir-β-endorphin (ir-β-END) content. Injection of 0·5 units insulin/kg lowered (P < 0·001) plasma glucose from 4·9 ± 0·3 mmol/l (mean ± s.d., saline controls) to 2·3 ± 0·5 mmol/l, coincident with increasing ir-ACTH (9·5 ± 3·1 to 106 ± 54 pmol/l), cortisol (52 ± 27 to 221± 27 nmol/l), ir-β-LPH (not detectable to 34 ± 18 pmol/l) and ir-β-END (not detectable to 52 ± 22 pmol/l). Plasma ir-α-MSH concentrations were not affected by insulin. Pretreatment with dexamethasone abolished the ir-ACTH, cortisol, ir-β-LPH and ir-β-END increases in response to 0·75 units insulin/kg. Haloperidol (1 mg/kg) increased (P < 0·01) plasma ir-ACTH (to 103 ± 63 pmol/l), cortisol (to 243 ± 11 nmol/l), ir-β-LPH (to 16 ± 6 pmol/l), ir-β-END (to 136 ± 73 pmol/l) and additionally raised ir-α-MSH (7 ± 8 pmol/l in saline controls to 131 ± 80 pmol/l after haloperidol). Pretreatment with dexamethasone significantly (P < 0·01 ) reduced the plasma ir-ACTH (96%), cortisol (93%), ir-β-LPH (100%) and ir-β-END (55%) response to haloperidol, but the ir-α-MSH increase (117 ± 81 pmol/l) was not affected.

The pituitary distribution of ir-β-END-like peptides was determined in tissue obtained from one healthy mongrel dog. Following G-50 gel filtration chromatography of HCl extracts, 40% of the total immunoreactivity determined in an extract of pars distalis eluted near the position of human β-LPH while 60% eluted near human β-END(1–31). In contrast, over 95% of ir-β-END eluted near β-END(1–31) in the tissue extract prepared from the neurointermediate lobe.

From the in-vivo data, it appears that insulin-induced hypoglycaemia selectively activates POMC peptide secretion by the pars distalis in dogs and that this effect is totally suppressible by dexamethasone. In contrast, haloperidol appears to activate secretion of POMC peptide from both the pars distalis and pars intermedia. The dog pars distalis secretes a mixture of ir-β-LPH and ir-β-END while the pars intermedia preferentially secretes ir-β-END.

J. Endocr. (1988) 117, 91–96
β-Core fragments are contaminants of the World Health Organization Reference Preparations of human choriogonadotrophin and its α-subunit
Authors: Wehmann R. E. , Blithe D. L. , Akar A. H. , Nisula B. C.
Published: December 2008

Highly purified preparations of human choriogonadotrophin (hCG), hCGα and hCGβ, including those preparations which are being distributed by the World Health Organization as International Standards, cross-reacted in a new radioimmunoassay with increased relative specificity for the β-core fragment of hCG. A major portion of the β-core immunoreactivity in the hCG and hCGα preparations eluted from Sephadex G-100 in a position (approximate apparent molecular size 15 000–18 000) corresponding to that of purified β-core fragment prepared from pregnancy urine. However, in the case of hCGβ-subunit preparations, virtually all of the β-core cross-reacting material eluted from Sephadex G-100 in the same fractions as the native hCGβ-subunit. Quantitatively, the cross-reacting β-core material accounts for less than 1% (w/w) of the total hCG or subunit immunoreactivity, as measured by conventional radioimmunoassays. The presence of the β-core fragments as discrete molecular components of the hCG and hCGα preparations should be borne in mind when these preparations are used to calibrate new radioimmunoassays for hCG-related molecules.

J. Endocr. (1988) 117, 147–152
Inadequate function of corpora lutea following the induction of ovulation with monensin and FSH in seasonally anoestrous ewes
Authors: Atkinson S.
Published: December 2008

Sixteen ewes in mid-seasonal anoestrus were stimulated to ovulate using sequential injections of FSH (total dose 10 mg) over a 4-day period. Half of the ewes received a dietary growth promotant (monensin) known to enhance the ovarian response to exogenous gonadotrophins. The ewes were ovariectomized on day 5 or 11 (day 0 = the initiation of FSH treatment). Serial blood samples were taken in half of the ewes to determine peripheral concentrations of LH and a single sample of ovarian venous blood was collected before ovariectomy. All luteal structures were dissected from the ovaries, counted and incubated in vitro to determine progesterone production. The luteal structures were then examined histologically for the abundance of luteal cells.

The physical appearance of the ovary, along with plasma concentrations of LH and ovarian venous oestradiol indicated that the monensin-treated ewes ovulated before control ewes. The corpora lutea from control ewes produced significantly (P <0·05) more progesterone than did the corpora lutea from the monensin-treated group. Furthermore, only 7% of the remaining luteal structures in the monensin-treated group produced significant amounts of progesterone on day 11, whereas 61% of the luteal structures in the control group were actively secreting progesterone. The mean number of granulosa cells in the follicles was similar at ovulation in the two groups, but the mean numbers of large and small luteal cells were significantly (P <0·05) lower in luteal structures from the monensin-treated ewes than in those from the control ewes. It is therefore postulated that inadequate corpora lutea function following precocious ovulation is due to a lack of luteal cell development formed after premature luteinization.

J. Endocr. (1988) 117, 167–172
Induction of LH hypersecretion in cyclic rats during the afternoon of oestrus by oestrogen in conjunction with progesterone antagonism or opioidergic blockade
Authors: Lustig R. H. , Pfaff D. W. , Fishman J.
Published: December 2008

The pro-oestrous secretion of progesterone that follows the LH surge in the rat limits the expression of the daily signal for LH surge initiation until the following oestrous cycle. This study explored the role of endogenous opioid peptides in the extinction by progesterone of the signal for the LH surge induced by oestrogen. Intact cyclic rats underwent external jugular venous cannulation on dioestrus, and were allowed to elicit a spontaneous pro-oestrous LH surge. On the afternoon of pro-oestrus, rats received an s.c. injection of oestradiol and an s.c. injection of either oil, 17β-hydroxy-11β-(4-dimethylaminophenyl)17α-(prop-1-ynyl)oestra-4,9,dien-3-one (RU 486; a synthetic anti-progestin), or N-cyclopropylmethyl-6-desoxy-6-methylene-noroxy-morphone (nalmefene; a long-acting opiate antagonist). Repeat doses of each were administered on the morning of oestrus to maintain increased oestrogen levels, and either progesterone or opioidergic blockade. Plasma was obtained from 13.00 to 19.00 h on oestrus for determination of the concentration of rat LH.

Rats treated with oestradiol alone demonstrated consistently low concentrations of LH throughout the afternoon of oestrus. Rats treated with both oestradiol and either RU 486 or nalmefene demonstrated spontaneous augmentations of rat LH concentration during the afternoon of oestrus, which, although of diminished amplitude as compared with that seen in pro-oestrus, were consistent with a reactivation of the LH surge-generating mechanism. Rats treated with nalmefene in the absence of oestradiol were unable to augment LH secretion spontaneously.

These experiments suggest that antagonism of progesterone action at the time of the LH surge prevents the extinction of the LH surge signal, so that it may be reactivated the next day by exogenous oestrogen. They similarly demonstrate that persistent opioidergic antagonism will permit oestrogen to reactivate the daily LH surge signal. The similar properties of an anti-progestin and an anti-opiate in this study suggest that the pro-oestrous progesterone rise extinguishes consecutive daily LH surges, in part, through increases in opioidergic tone.

J. Endocr. (1988) 117, 229–235
Vitamin D-induction of secretory responses in rat pituitary tumour (GH4C1) cells
Authors: Wark J. D. , Gurtler V.
Published: December 2008

1,25-Dihydroxyvitamin D3(1,25-(OH)2D3) selectively enhances prolactin gene expression in GH4C1 clonal rat pituitary tumour cells. Because this effect requires extracellular Ca2+, we studied the effect of 1,25-(OH)2D3 on another Ca2+-dependent process, agonist-induced hormone secretion. Pretreatment with 1,25-(OH)2D3 (1 nmol/l) caused at least 25-fold sensitization of GH4C1 cells to the voltage-sensitive Ca2+ channel agonist BAY K 8644 (methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyridine-5-carboxylate) as a prolactin secretagogue. This inductive effect of 1,25-(OH)2D3 followed a similar time-course to the enhancement of prolactin production. 1,25-(OH)2D3 had no effect on basal or BAY K 8644-induced 45Ca2+ uptake. The Ca2+-selective divalent cation ionophore 11,19,21-trihydroxy-4,6,8,12,14,18,20-heptamethyl-9-oxo-22-(tetrahydro-5 methyl-5-tetra hydro-5-(1-hydroxyethyl)-5-methyl-2-furanyl)-10,16-docosadienoic acid (ionomycin; 12 nmol/l–1·2 μmol/l) caused no significant increase in prolactin secretion in the absence of 1,25-(OH)2D3, but in cells treated with 1,25-(OH)2D3-(1 nmol/l), it increased prolactin secretion by 73% at 12 nmol/l and by a maximum of 98% at 0·12 μmol/l. These data demonstrate that vitamin D markedly enhances the responsiveness of GH4C1 functional pituitary tumour cells to two secretagogues which acts primarily through Ca2+-dependent mechanisms. They support the proposal that 1,25-(OH)2D3 acts in this cultured cell model either by effecting a redistribution of intracellular Ca2+ or by increasing the response of a Ca2+ -sensitive effector system, but not by enhancing agonist-induced Ca2+ uptake.

J. Endocr. (1988) 117, 293–298
Expression of androgen receptors and prostatic steroid-binding protein during development of the rat ventral prostate
Authors: Zhang Y. L. , Zhou Z. X. , Zhang Y. D. , Parker M. G.
Published: December 2008

Prostatic steroid-binding protein (PSBP) mRNAs transcribed from the three genes C1, C2 and C3 were quantitated in neonatal rat ventral prostate by Northern blot analysis. Transcription was initiated at day 14 for C1 and C2 and day 10 for C3, and reached mature levels by day 21 for C1 and C2 and day 28 for C3. The changes of both cytoplasmic and nuclear prostatic androgen receptors in 10- to 150-day-old rats were investigated by radioligand assay and showed a fivefold transient increase between days 10 and 28. Thus there was a good correlation between the onset of PSBP gene expression and the transient increase in androgen receptors; increases in receptor concentration may be a prerequisite for changes in gene expression.

J. Endocr. (1988) 117, 361–366
Aldosterone in colonic potassium adaptation in rats
Authors: Edmonds C. J. , Willis C. L.
Published: December 2008

The influence of adrenalectomy and administration of aldosterone on potassium secretion by colonic epithelium was studied in vivo in rats, particularly in relation to potassium adaptation (induced by feeding a potassium-rich diet) and the response to acute i.v. administration of a potassium load. Adrenalectomy (rats maintained on dexamethasone and saline) impaired the development of potassium adaptation or considerably reduced it if the rats had been previously adapted. The partial adaptation observed in the adrenalectomized rats may be related to the increased plasma potassium concentration developed when these rats received the potassium-rich diet.

Within 2 h of acute aldosterone administration, the response of the potassium secretion rate to acute potassium loading in adrenalectomized rats was significantly improved. When aldosterone (2 μg/day per 100 g body weight, given by osmotic minipump) was added to the replacement treatment, the plasma concentration of potassium was similar to that of the intact rats, and both potassium adaptation and the response to the acute potassium load were completely restored. Transepithelial potential difference and sodium transport were not stimulated, being similar to the values in intact rats. Considerable changes in potassium secretion induced by acute potassium loading did not significantly affect sodium transport.

The findings suggest that the sodium and potassium epithelial pathways are, to a large extent, independently influenced by aldosterone. Aldosterone appears to be essential for complete adaptation and, in a relatively low dose, can completely restore potassium adaptation and the response to acute potassium loads in adrenalectomized rats.

J. Endocr. (1988) 117, 379–386
Stimulation of cortisol production in isolated bovine zona fasciculata cells by phorbol ester: role of ion fluxes
Authors: Kenyon C. J. , Anyaorah L. , Woodburn L. , Connell J. M. C. , Fraser R.
Published: December 2008

The role of protein kinase C activation in the control of cortisol synthesis was studied using the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA). Bovine zona fasciculata cells were incubated with various concentrations of TPA in the presence and absence of EGTA, verapamil or nitrendipine to see whether cortisol stimulation was dependent on extracellular calcium ions. When free extracellular concentration of Ca2+ was reduced to approximately 10 μmol/l the cortisol response at all concentrations of TPA was reduced by approximately 25% indicating that protein kinase C activation is only partially dependent on extracellular calcium ions. This is confirmed by the effects of the voltage-dependant calcium channel blocker verapamil, which partially inhibited the cortisol response to a maximally effective concentration of TPA (1 μmol/l). However, a second channel blocker, nitrendipine, proved to be ten times more potent than verapamil and totally inhibited the TPA response. The partial effects of EGTA and verapamil and the contrast between verapamil and nitrendipine do not exclude the possibility that intracellular calcium ions are important in protein kinase C activation and may indicate that nitrendipine has better access to an additional site of inhibitory action than verapamil. It is significant that the ionophore A23187, which facilitates Ca2+ entry independently of voltage-sensitive channels, failed to overcome the inhibitory effects of nitrendipine in TPA-stimulated cells.

In some other tissues, the effects of protein kinase C activation are mediated by the opening of Na+/H+ exchange ports. The involvement of this port in the cortisol response has been tested by incubating TAP-and ACTH-treated cells with amiloride, an inhibitor of Na+/H+ exchange. It would seem unlikely that the steroidogenic effects of TPA are mediated by altered Na+/H+ exchange because, at the high concentration of amiloride used to block cortisol synthesis (1 mmol/l), non-specific side effects may occur and also because amiloride at this concentration inhibited the cortisol response to ACTH whose mechanism of action is not solely dependent on protein kinase C activation.

Cells were also incubated with increasing concentration of TPA in the presence and absence of ACTH and angiotensin. TPA did not further stimulate ACTH-treated cells and at 0·32 μmol/l inhibited cortisol synthesis. The effects of angiotensin and TPA were additive which suggests that the steroidogenic effects of angiotensin II are largely independent of protein kinase C activation.

J. Endocr. (1988) 117, 423–429
Effect of difluoromethylornithine on the LH surge and subsequent ovulation in the rat
Authors: Nicholson S. A. , Aslam M. , Chuang T. T. , Gillham B. , Jones M. T.
Published: December 2008

Female Wistar-derived rats with regular oestrous cycles were injected s.c. at 15.00 h on pro-oestrus with difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase. The drug (10–100 mg/rat) caused a dose-related reduction in the concentration of LH in plasma taken at 19.00 h (the time of the peak of the LH surge in this colony). There was also a dose-related reduction in the pituitary content of total polyamines. The reduction in the plasma concentration of LH was not due to the shifting of the time of the peak of the surge, as concentrations were significantly lower than control from 17.00 to 21.00 h, the overall reduction in total LH release being approximately 50%. The number of ova in the oviducts at 06.00 h next morning was significantly reduced by treatment with 50 mg DFMO/rat, by an average of 70%.

Injection of DFMO enhanced the fall in plasma oestradiol concentrations seen between 15.00 and 19.00 h, in a dose-related manner. It also prevented the rise in progesterone concentrations seen in control animals during this period. The ability of DFMO to prevent the rise in plasma concentrations of LH was not secondary to the effects of the drug on ovarian steroid production because DFMO also significantly reduced the LH surge in animals ovariectomized on dioestrus and given appropriate replacement injections of oestradiol and progesterone.

It seems possible that part of the action of DFMO is exercised at the hypothalamus, since when 50 mg DFMO/rat was given either 2 or 4 h before the expected peak of the LH surge, the LHRH content of the hypothalamus was significantly reduced at that time. These results suggest that activation of ornithine decarboxylase is a necessary prerequisite for a normal LH surge, and that this activation is steroid-dependent. This conclusion is borne out by results from direct observations on the activity of the enzyme in pituitary tissue incubated in vitro.

J. Endocr. (1988) 117, 447–453
The natural history of adrenal function in autoimmune patients with adrenal autoantibodies
Authors: Betterle C. , Scalici C. , Presotto F. , Pedini B. , Moro L. , Rigon F. , Mantero F.
Published: December 2008

Adrenal autoantibodies (AA) were found in 23 of 2571 (0·9%) patients with organ-specific autoimmune diseases, in one of 632 first-degree relatives of insulin-dependent diabetic patients, and in none of 375 normal controls. In AA-positive subjects the prevalence of human leucocyte antigens (HLA)-A1, -B8 and -DR3 was significantly higher with respect to the general population. Two groups were followed (15 subjects persistently positive for AA and 51 negative subjects) for a mean period of 3·2 years. Yearly tests were made for AA and adrenal function. Of the 15 subjects persistently positive for AA, six developed Addison's disease after a period varying from 6 months to 10 years. Of the 51 subjects initially negative, two became positive during follow-up, and one of these developed Addison's disease 16 months later. In contrast, all the remaining 49 persistently negative subjects maintained normal adrenal function tests. Overall, of the 17 positive subjects, seven (41%) developed Addison's disease, three (18%) showed various degrees of subclinical adrenocortical failure and the remaining seven maintained normal glandular function. In the positive patients the yearly incidence of detriment in adrenal function was 19%. Patients who developed Addison's disease showed significant association with HLA-B8 phenotype. The development from normal adrenocortical function to overt Addison's disease seemed to progress through four distinct stages of functional impairment: increased plasma renin activity with normal/low aldosterone (stage 1), low cortisol response after i.v. administration of ACTH (stage 2), increased ACTH (stage 3), and low basal cortisol (stage 4). Thus, idiopathic Addison's disease appears to be a chronic autoimmune disorder with a genetic predisposition and a long preclinical period marked by the presence of AA. Steroid-producing cell antibodies were also evaluated but they were not found to be markers of gonadal dysfunction.

J. Endocr. (1988) 117, 467–475
The isolation, purification and some properties of pheromaxein, the pheromonal steroid-binding protein, in porcine submaxillary glands and saliva
Authors: Booth W. D. , White C. A.
Published: December 2008

Pheromaxein, the 16-androstene steroid-binding protein with a relative molecular mass of 15 000 was isolated in sub-milligram quantities from the submaxillary gland and saliva of the Gottingen miniature boar, after a fourfold purification involving the following methods: ultrafiltration for submaxillary gland cytosols and ethanol precipitation for saliva, Concanavalin-A-Sepharose affinity chromatography, sodium dodecyl sulphate polyacrylamide gel electrophoresis, 'Extractigel-D' affinity chromatography (to remove sodium dodecyl sulphate) and fast protein-liquid chromatography. Yields of purified pheromaxein obtained after fast protein-liquid chromatography represented 10–20% of total protein present in an ultrafiltrate of a submaxillary gland cytosol. Fast protein-liquid chromatography separated the α- and β-charge isomers of pheromaxein which were shown to have isoelectric points of 4·78 and 5·35 respectively on flat-bed isoelectric focusing. Some data are provided for the variable occurrence of the isomeric forms of pheromaxein in relation to different breeds of pig. Five 16-unsaturated steroids showed the highest binding to pheromaxein. Other steroids of the 5α- and 5β-androstane series also showed some binding to pheromaxein, i.e. 17β-hydroxy-5α-androstan-3-one (19·2%), with 5α-androstan-3-one, which has a similar urinous odour to 5α-androst-16-en-3-one, showing the greatest binding (42·6%) relative to 5α-androst-16-en-3-one (100%).

J. Endocr. (1988) 118, 47–57
Early changes in serum concentrations of somatomedin-C induced by dietary protein deprivation in rats: contributions of growth hormone receptor and post-receptor defects
Authors: Maiter D. , Maes M. , Underwood L. E. , Fliesen T. , Gerard G. , Ketelslegers J.-M.
Published: December 2008

To define the mechanism(s) for the decrease of somatomedin concentrations in acute protein malnutrition, we have assessed the relationships between serum immunoreactive somatomedin-C/insulin-like growth factor-I (Sm-C/IGF-I), serum immunoreactive GH and total (MgCl2-treated homogenates) as well as free (water-treated homogenates) liver somatogenic (GH) binding sites in growing rats fed a 5% protein diet for 12 or 24 h and given an s.c. injection(s) of rat GH (rGH) or saline. Control rats were fed a 15% protein diet and injected with rGH or saline.

After 12 and 24 h of protein restriction, body weight was 6·9 and 8·2% below controls respectively (P < 0·001), while Sm-C/IGF-I concentrations were reduced by 58 and 66% respectively (P < 0·001 vs controls). Serum GH concentrations were not affected by the low protein intake. Furthermore, injection(s) of 50–100 μg rGH failed to raise serum Sm-C/IGF-I concentrations in the protein-deficient animals. The number of total and free GH-binding sites was modestly (15–20%) decreased at 12 and 24 h in the protein-restricted rats. Serum Sm-C/IGF-I concentrations correlated weakly with free and total binding sites (r = 0·48 and 0·38 respectively). Affinity constants of GH-binding sites were not changed by protein restriction.

The profound reduction in Sm-C/IGF-I concentrations within a few hours of beginning protein restriction, and the discordance between this reduction and the small decline in somatogenic binding sites, suggests that, in addition to GH receptor loss, a postreceptor defect may participate in the GH resistance occurring in the early stages of protein deficiency.

J. Endocr. (1988) 118, 113–120
Effect of the suckling stimulus on daily LH surges induced by chronic oestrogen treatment in ovariectomized lactating rats
Authors: Tsukamura H. , Maeda K.-I. , Yokoyama A.
Published: December 2008

Effects of the suckling stimulus on the daily LH surge induced by chronic oestrogen treatment were examined in ovariectomized lactating rats. Wistar– Imamichi strain rats were kept under 14 h light:10 h darkness (lights on at 05.00 h). Litter size was adjusted to eight on day 1 (day 0 = day of parturition) and ovariectomy performed on day 2. Lactating rats deprived of their litters on day 0 served as non-lactating controls. Silicone elastomer tubing filled with oestradiol was implanted on day 6 or 15. Blood samples were collected through an indwelling cannula at 10.00 and 17.00 h on each day after implantation to detect daily LH surges. Daily LH surges occurred in the late afternoon in both lactating and non-lactating rats implanted with oestradiol on day 6 or 15. The amplitude of daily LH surges in lactating rats implanted on day 6 declined much more rapidly than in non-lactating rats implanted on day 6, but no significant difference was found in the profile of the LH surge between lactating and non-lactating rats implanted on day 15. Pituitary LH contents just before the daily LH surge (12.00–12.30 h) 4 days after implantation in lactating rats implanted with oestradiol on day 6 were significantly less than those in non-lactating rats implanted with oestradiol on day 6 or 15 and in lactating rats implanted on day 15. These results suggest that the mechanisms responsible for the oestradiol-induced LH surge were not impaired by the suckling stimulus, and that a rapid decline of the amplitude of LH surges observed in mid-lactation could be ascribed to the small amount of LH stored in the pituitary.

J. Endocr. (1988) 118, 311–316
Adrenal glands alter the concentration of oestradiol-17β and its receptor in the uterus of ovariectomized ewes
Authors: Atkinson S. , Adams N. R.
Published: December 2008

To investigate the effects of adrenal hormones on oestrogen activity in the uterus, ovariectomized ewes were either adrenalectomized, administered glucocorticoid-like preparations (CORT), or remained as controls. The adrenalectomized ewes were maintained with a corticoid-replacement therapy and monitored daily for plasma glucose and Na+/K+ concentrations. Blood samples were collected from all ewes at 15-min intervals for 4 h and assayed for LH and FSH. The adrenalectomized ewes were killed 9 days after adrenalectomy, while the CORT ewes were killed after 3 weeks of drug therapy. The control ewes were killed simultaneously with the CORT ewes. Uterine tissues were homogenized and the numbers of oestradiol receptors and tissue concentrations of oestradiol-17β were measured. The adrenalectomized ewes had significantly higher concentrations of cytosolic oestrogen receptors in the uterus than did the control ewes, which had significantly higher concentrations than the CORT ewes (0·95±0·06, 0·76 ± 0·02 and 0·60±0·02 (s.e.m.) μmol/kg protein respectively). The concentrations of oestradiol-17β measured in uterine tissues were significantly lower in adrenalectomized and CORT ewes than in control ewes (37·4±5·5, 61·7±25·7 and 135·5 ± 12·8 pmol/kg respectively). There were no significant differences between any groups in the peripheral concentrations of LH or FSH. These results indicate that the adrenal gland affects the concentrations of both oestrogen and its receptor in the uterus of ovariectomized ewes, probably by different mechanisms. These effects are not mediated by gonadotrophins.

J. Endocr. (1988) 118, 375–380
The influence of plasma concentrations of tri-iodothyronine on the acute increases in insulin and muscle protein synthesis in the refed fasted rat
Authors: Millward D. J. , Brown J. G. , van Bueren J.
Published: December 2008

To examine whether the low plasma levels of triiodothyronine (T3) in fasted rats might limit the recovery of muscle protein synthesis on refeeding, rats were fasted for either 3 or 4 days and refed with or without pretreatment with thyroid hormones. Fasting suppressed T3 levels, plasma insulin and the rate of the translational phase of muscle protein synthesis (KRNA; the rate per unit RNA), especially after the 4-day fast. On refeeding, plasma T3 levels remained low for more than 3 h after the 3-day fast and for more than 8 h after the 4-day fast. Insulin concentrations increased within the first hour of refeeding, eventually achieving supranormal concentrations after the 3-day fast. The KRNA increased within the first hour of refeeding, achieving well-fed control values by 3 h after the 3-day fast or 24 h after the 4-day fast. The increases in KRNA were significantly correlated with the increases in insulin at low insulin concentrations, achieving a plateau value at 150 pmol/l, so that further increases in insulin were not associated with any further increases in protein synthesis. Pretreatment with thyroid hormone induced increased T3 levels which were maintained for up to 8 h of refeeding. This had no effect on the responses of either insulin or protein synthesis to refeeding after the 3-day fast, but did result in an acceleration of the recovery in the KRNA and plasma insulin levels in the rats fasted for 4 days. Analysis of the insulin–KRNA relationship showed no evidence for any increase in the insulin sensitivity of muscle protein synthesis with thyroid pretreatment, the initial stimulation of protein synthesis on refeeding the rats fasted for 4 days reflecting increased insulin secretion. Since in the untreated animals, insulin secretion on refeeding was also correlated with T3 levels, these results are consistent with the previously reported thyroidal dependence of insulin secretion.

J. Endocr. (1988) 118, 417–422
Regulation of aldosterone secretion by avian adrenocortical cells
Authors: Rosenberg J. , Pines M. , Hurwitz S.
Published: December 2008

Dispersed chick adrenocortical cells were incubated with mammalian and avian angiotensin-II, Ca2+, K+, verapamil, nifedipine, Ca2+ ionophore (A23187), protein kinase-C activator (phorbol 12-myristate 13-acetate; TPA), atrial natriuretic peptide (ANP), sodium nitroprusside (SNP) and ACTH. Secretion of aldosterone and corticosterone, and accumulation of cyclic nucleotides were assessed.

Secretion of aldosterone was not affected by angiotensin-II, Ca2+ channel blockers, Ca2+ ionophore or TPA. ANP stimulated production of cyclic GMP (cGMP), and inhibited aldosterone secretion with a similar dose–response relationship. SNP also stimulated cGMP production and inhibited the ACTH-stimulated aldosterone secretion. The results indicate that ANP is an inhibitor of aldosterone secretion in birds and suggest that this inhibition is mediated by cGMP. In contrast to mammalian glomerulosa cells, angiotensin-II and the calcium-inositol phosphate-protein kinase C pathway appear not to be involved in the regulation of aldosterone secretion by avian adrenal cells.

J. Endocr. (1988) 118, 447–453
Long-term effects of a gonadotrophin-releasing hormone agonist ([d-Ser(But)6]GnRH(1–9)nonapeptide-ethylamide) on gonadotrophin secretion from human pituitary gonadotroph cell adenomas in vitro
Authors: Daniels M. , Newland P. , Dunn J. , Kendall-Taylor P. , White M. C.
Published: December 2008

We have studied the effects of TRH and native gonadotrophin-releasing hormone (GnRH), and of a GnRH agonist (Buserelin; [d-Ser(But)6]GnRH(1–9) nonapeptide-ethylamide), on LH, FSH, α subunit and LH-β subunit secretion from three human gonadotrophin-secreting pituitary adenomas in dispersed cell culture. During a 24 h study, treatment with 276 nmol TRH/1 resulted in a significant (P < 0·05) stimulated release of FSH and α subunit from all three adenomas, and LH from the two adenomas secreting detectable concentrations of this glycoprotein; treatment with 85 nmol GnRH/l significantly (P < 0·05) stimulated the release of α subunit from all three, but FSH from only two and LH from only one adenoma. During a long-term 28-day study, basal FSH and α subunit concentrations were maintained, but secretion of LH, and LH-β (detectable from one tumour only), declined with time from two of the three adenomas. Addition of Buserelin to the cultures resulted in the continuous (P < 0·05) stimulation of α subunit secretion from all three adenomas, and of LH and FSH from two, whilst a transient stimulatory effect on LH and FSH secretion was seen from a third adenoma, with subsequent secretion rates declining towards control values. These data show that human gonadotrophin-secreting adenomas demonstrate variable stimulatory responses to hypothalamic TRH and GnRH, and that during chronic treatment with a GnRH agonist the anticipated desensitizing effect of the drug was not observed in two out of three adenomas studied. The mechanism for this is not clear, but such drugs are unlikely to be of therapeutic value in the management of gonadotrophin-secreting tumours. The data also suggest that GnRH and GnRH agonists have a differential effect on the in-vitro release of intact gonadotrophins and the common α subunit.

J. Endocr. (1988) 118, 491–496
Leukotriene release by human fetal membranes, placenta and decidua in relation to parturition
Authors: Rees M. C. P. , Di Marzo V. , Bernal A. Lopez , Tippins J. R. , Morris H. R. , Turnbull A. C.
Published: December 2008

Complete placentas and membranes were obtained from women after uncomplicated singleton pregnancies. Six were collected after labour at term, six after preterm labour and six after elective Caesarean section at term. Leukotriene C4 (LTC4), leukotriene D4 (LTD4) and leukotriene E4 (LTE4) release was examined using a short-term incubation technique. Release by amnion was significantly higher than that by the other tissues for the three modes of delivery. Comparison of LTC4, LTD4 and LTE4 release by individual tissues with regard to the type of delivery showed no significant difference.

J. Endocr. (1988) 118, 497–500