bluuebunny/crossref_metadata_2025 huggingface dataset:
Vasoactive intestinal peptide and the stimulation of lactotroph growth by oestradiol in rats
Authors: Prysor-Jones R. A. , Silverlight J. J. , Kennedy S. J. , Jenkins J. S.
Published: December 2008

Treatment with a high dose of oestradiol for 6 months caused hyperprolactinaemia and pituitary hyperplasia in female Wistar–Furth rats. Changes in the vasoactive intestinal peptide (VIP) and dopamine content of the hypothalamus and pituitary were also found. The hypothalamic dopamine concentration was only slightly reduced and, although the concentration of dopamine in the pituitary was less in treated animals, the total pituitary content was increased. The concentration of VIP in the pituitary was increased by oestradiol treatment but decreased in the non-median eminence hypothalamus. In the median eminence the VIP content was increased by oestradiol treatment and the amount present correlated positively and significantly with pituitary wet weight in animals treated with both oestradiol and fluphenazine. In Fischer 344 rats, oestradiol produced greater incremental changes in pituitary wet weight and plasma concentrations of prolactin than in Wistar controls and the increase in the pituitary concentration of VIP was five times greater. Although peptide turnover has not been measured, these results suggest that oestradiol, as well as having a direct action, stimulates pituitary lactotrophs by increasing pituitary concentrations of VIP.

J. Endocr. (1988) 116, 259–265
Diurnal variation in the effect of potassium depolarization on vasoactive intestinal polypeptide release from rat hypothalamus: a possible role for adrenaline
Authors: Burns G. , Brown B. L. , Dobson P. R. M.
Published: December 2008

We have previously reported a lack of effect of a depolarizing concentration of K+ on the release of vasoactive intestinal polypeptide (VIP) from the perifused rat hypothalamus, and suggested that this was due to the presence of an endogenous inhibitor of the release of VIP. In this study we report that the VIP response to K+ was restored if the hypothalami were obtained from animals killed during the dark phase of the light–dark cycle. Adrenaline blocked the K+-stimulated release of VIP when used at a concentration of 0·1 μmol/l; however, at a higher concentration (10 μmol/l) adrenaline stimulated the basal release of VIP. The use of specific receptor antagonists indicated that this dual effect of adrenaline was mediated through two distinct receptors, a stimulatory β-receptor and an inhibitory α2-receptor. The suggestion that adrenaline might be the endogenous inhibitor of the release of VIP, mediating the diurnal variation in the effect of K+, was supported by studies where 50 mmol K+/l was perifused concomitantly with an α2-antagonist, restoring the VIP response to K+ in light-phase hypothalami. In conclusion, adrenaline has a dual role in the control of VIP release and may function to inhibit the K+-stimulated release of VIP in our system.

J. Endocr. (1988) 116, 335–341
Quantitative in-situ hybridization histochemistry in the rat pituitary gland: effect of bromocriptine on prolactin and pro-opiomelanocortin gene expression
Authors: Levy A. , Lightman S. L.
Published: December 2008

The temporal effect of orally administered bromocriptine on pro-opiomelanocortin (POMC) and prolactin gene expression in male Sprague–Dawley rats was examined using in-situ hybridization histochemistry. Messenger RNA in the anterior and intermediate lobes could be clearly delineated in each section. Administration of bromocriptine resulted in a reduction in hybridization of 35S-labelled cDNA probe to prolactin mRNA from 0·69 × 1012 to 0·29 × 1012 copies bound/g after 150 h. POMC mRNA in the anterior lobe remained unchanged with 0·08 × 1012 copies of probe bound/g for the duration of the experiment, while in the intermediate lobe it decreased from 2·44 × 1012 to 0·44 × 1012 copies of probe bound/g at 150 h. The rate of reduction in intermediate lobe POMC mRNA was similar to that of prolactin mRNA for the first 24 h but was subsequently more rapid and more profound, falling to 20% of the control value at 84 h and to 18% at 150 h.

J. Endocr. (1988) 118, 205–210
Ascorbic acid potentiates the inhibitory effect of dopamine on prolactin release in primary cultured rat pituitary cells
Authors: Shin S. H. , Stirling R.
Published: December 2008

The chemical structure of dopamine includes an ortho-catechol group which is labile to oxidizing agents. Ascorbic acid, a reducing agent, has in the past been added to the incubation medium in order to protect dopamine against oxidation. However, there has been no thorough examination of the biological effect of ascorbic acid on prolactin release. In this present study we have shown that ascorbic acid has neither a stimulatory nor an inhibitory effect on prolactin release but reduces by approximately two orders of magnitude the concentration of dopamine necessary to inhibit prolactin release from cultured anterior pituitary cells. The strong potentiation effect of ascorbic acid was reproduced using apomorphine. We compared the effect of ascorbic acid and isoascorbic acid on dopamine inhibition of prolactin release. Isoascorbic acid is an epimer of ascorbic acid, having the same reduction–oxidation potential as ascorbic acid, but is less biologically active. Isoascorbic acid was less effective in potentiating the dopaminergic effect than was ascorbic acid, which supports the notion that potentiation by ascorbic acid is not entirely due to its reducing property.

In order to dissociate further the chemical protection of dopamine from the biological potentiation, the inhibitory effects of freshly made and 3-h-old dopamine solutions were compared. Neither one of the two solutions contained any ascorbic acid, yet the two solutions did not show any difference in their ability to inhibit prolactin release during the 3-h incubation period, indicating that no significant amount of dopamine was oxidized. The minimum effective concentration of ascorbic acid necessary to demonstrate potentiation was between 0·001 and 0·01 mmol/l. The potentiation effect was shown after 1, 2, or 3 h of exposure to dopamine, and was evident in both 2- and 6-day-old cultured cells.

The effect of ascorbic acid can either be a pharmacological potentiation or a physiological effect on the primary cultured pituitary cells. However, it is quite clear that ascorbic acid is not a simple anti-oxidant but produces a strong potentiating effect on the dopaminergic inhibition of prolactin release by some other means.

J. Endocr. (1988) 118, 287–294
Effects of an aromatase inhibitor on testosterone-induced inhibition of thymus growth in immature female rats
Authors: Greenstein B. D. , Mander B. J. , Fitzpatrick F. T. A.
Published: December 2008

The hypothesis was tested that the inhibitory action of testosterone on thymus growth is mediated by its metabolism to oestradiol. Immature female rats were given s.c. implants of silicone elastomer tubing containing 5 or 20 mg testosterone alone, or together with 25 or 50 mg of an aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD). Some rats received implants containing 5 mg oestradiol or 5 mg dihydrotestosterone (DHT). After 14 days the thymus was removed and weighed. Body weight gain was similar in animals treated with empty implants, or 5 mg testosterone or DHT, or with ATD alone. The combination of testosterone and ATD significantly increased body weight gain, and oestradiol significantly decreased it. Thymus growth was inhibited by both doses of testosterone and by oestradiol, but not by DHT. ATD alone did not inhibit thymus growth, nor did the lower dose of ATD inhibit the action of testosterone. The higher dose of ATD did, however, significantly reduce the inhibitory action of testosterone on the thymus. The inhibitory action of testosterone on the growing thymus may be due, at least in part, to its conversion to oestradiol.

J. Endocr. (1988) 119, 65–67
Inhibition of phospholipase A2 isoenzymes in human endometrium by mefenamic acid and indomethacin: modulation by calcium ions
Authors: Bonney R. C. , Qizilbash S. T. , Franks S.
Published: December 2008

The inhibition of endometrial phospholipase A2 activity by the non-steroidal anti-inflammatory agents mefenamic acid and indomethacin was studied over the concentration range 1 mmol/l–0·1 μmol/l. Both phospholipase A2 type 1 (a calcium-dependent enzyme) and phospholipase A2 type 2 (a calciumindependent enzyme) were inhibited by mefenamic acid, but the magnitude of the inhibition was dependent on calcium concentration. Phospholipase A2 type 1 was inhibited 50% by 10 μmol mefenamic acid/1 in the presence of 1·25–5 mmol calcium/l, but a concentration of 2·2 mmol mefenamic acid/l was required for 50% inhibition in the absence of calcium. On the other hand, phospholipase A2 type 2 was inhibited 50% by 22 μmol mefenamic acid/1 in the absence of calcium and by 100 μmol mefenamic acid/l in the presence of calcium (2·5 mmol/l). Although indomethacin was a less effective inhibitor of phospholipase A2 activity, a similar relationship with calcium was demonstrated. However, indomethacin also had a stimulatory effect on phospholipase A2 type 1 activity in the absence of calcium. Our findings suggest that the two endometrial enzymes may be inhibited by different mechanisms and that the dependence of the enzyme on calcium for activation may be a contributing factor.

J. Endocr. (1988) 119, 141–145
Calcitonin gene-related peptide and calcitonin secretion from a human medullary thyroid carcinoma cell line: effects of ionomycin, phorbol ester and forskolin
Authors: Haller-Brem S. , Muff R. , Fischer J. A.
Published: December 2008

Calcitonin gene-related peptide (CGRP) and calcitonin are secreted together from medullary thyroid carcinoma (MTC) cells. Interactions of cytosolic free calcium concentration (Cai2+) and the protein kinase C and A pathways on the secretion of immunoreactive CGRP and calcitonin have been investigated in a human MTC cell line. Ionomycin (10 μmol/l) raised the concentration of Cai2+, concomitant with a transient stimulation of the secretion of CGRP and calcitonin. 12-O-tetradecanoylphorbol-13-acetate (TPA; 16 nmol/l) did not affect the concentration of Cai2+, but caused a gradual rise of the secretion of CGRP and calcitonin. Combined addition of 10 μmol ionomycin/1 and 16 nmol TPA/1 resulted in additive stimulation of CGRP and calcitonin secretory responses. Forskolin (10 μmol/l) alone did not change the concentration of Cai2+, marginally enhanced (P>0·1) the release of CGRP and calcitonin and increased by 23-fold the cellular levels of cyclic AMP (cAMP). Ionomycin and TPA did not change cellular cAMP. Forskolin synergistically enhanced (P<0·01) the ionomycin-induced early phase as well as the TPA-induced late phase of the CGRP and calcitonin secretory responses. In conclusion, increased concentrations of Cai2+ together with protein kinase C and A activation mediate the secretion of CGRP and calcitonin in MTC cells.

J. Endocr. (1988) 119, 147–152
The functional activity of hypothalamic 5-hydroxytryptamine neurones in broody bantam hens
Authors: Macnamee M. C. , Sharp P. J.
Published: December 2008

An assessment was made of the possible role of hypothalamic 5-hydroxytryptamine (5-HT) in the regulation of prolactin secretion in broody bantam hens. Prolactin secretion was stimulated less in incubating hens deprived of their nests for 24 h (nest-deprived) than in laying hens after administration of the 5-HT receptor agonist quipazine, or precursor 5-hydroxytryptophan. One type of 5-HT-binding site was found in the anterior and posterior hypothalami of out-of-lay, incubating and laying hens. Differences in prolactin secretion in these birds could not be accounted for by changes in the abundance of this type of 5-HT-binding site. Another type of 5-HT-binding site, with a higher density but lower affinity, was found in the anterior hypothalami of laying hens. No specific 5-HT-binding sites were found in the anterior pituitary gland.

The turnover rates of 5-HT were compared in the anterior and posterior hypothalami of laying, incubating and nest-deprived hens. The turnover rates were estimated from the rate of accumulation of 5-HT after inhibiting its catabolism using the monoamine oxidase inhibitor, pargyline, or by measuring the ratio of the concentrations of 5-HT and its major metabolite, 5-hydroxyindole acetic acid. Both methods of measurement gave the same results. The turnover of 5-HT was increased in the anterior but not posterior hypothalami of incubating hens when compared with laying or nest-deprived hens. There was also a significant increase in turnover of 5-HT in the posterior hypothalami in nest-deprived hens when compared with laying or incubating birds.

These results demonstrate a strong correlation between the function of 5-HT neurones in the hypothalamus and reproductive activity. They are consistent with the view that hypothalamic 5-HT is involved in the regulation of prolactin secretion.

Journal of Endocrinology (1989) 120, 125–134
Serum inhibin levels in normal men and men with testicular disorders
Authors: de Kretser D. M. , McLachlan R. I. , Robertson D. M. , Burger H. G.
Published: December 2008

Serum concentrations of inhibin, FSH and LH were measured in 39 normal men and 127 men with testicular disorders resulting in infertility. The infertile men were divided into groups on the basis of their mean sperm count, FSH levels and karyotype. The mean (±s.d) serum concentrations of inhibin in the normal men was 554 ± 156 U/l and did not differ significantly from those groups with oligospermia, azoospermia or Klinefelter's syndrome. Combined analyses of all groups did not reveal any significant correlation between serum concentrations of inhibin and FSH or with any other parameter measured. Serum concentrations of FSH and LH were positively correlated, and Leydig cell dysfunction, as evidenced by increased serum LH levels, low testosterone levels or a declining testosterone/LH ratio were found with severe spermatogenic damage. The failure of serum concentrations of inhibin to correlate with those of FSH levels or the degree of testicular damage raise questions as to the clinical value of this parameter alone.

Journal of Endocrinology (1989) 120, 517–523
Interruption of parturition in rats by morphine: a result of inhibition of oxytocin secretion
Authors: Russell J. A. , Gosden R. G. , Humphreys E. M. , Cutting R. , Fitzsimons N. , Johnston V. , Liddle S. , Scott S. , Stirland J. A.
Published: December 2008

Oxytocin secretion is inhibited by opioids, and oxytocin is important in parturition. The effects on parturition of morphine, a relatively selective μ-opioid receptor agonist, were studied in the rat. Morphine or vehicle with or without the opiate antagonist naloxone were administered immediately after the birth of the second pup and the subsequent course of parturition was recorded in a total of 80 rats. Both s.c. morphine (10 mg/kg) and intracerebroventricular (i.c.v.) morphine (18 μg through a previously implanted cannula) interrupted parturition, delaying the birth of the sixth pup after treatment to 187·3 ± 35·9 (s.e.m.) min and 195·4 ± 19·5 min respectively, compared with 46·4 ± 3·7 and 66·1 ± 17·5 min after vehicle alone. The dose of morphine given i.c.v. had no effect when given s.c. Naloxone given concurrently prevented the effects of morphine. Eventually the rate of parturition in the morphine-treated groups recovered. Perinatal pup mortality rate was not increased when morphine was given to the mothers, but it did inhibit the expression of normal intrapartum maternal behaviour.

Pup mortality was increased 48 h post partum by morphine given during parturition, and it reduced the proportion of rats with normal maternal behaviour 24 h post partum. Morphine did not affect spontaneous or oxytocin-stimulated contractile activity of the parturient uterus in vitro. The concentration of oxytocin in trunk blood plasma was decreased 40 min after i.c.v. morphine (24·3 ± 3·9 vs 39·3± 6·5 pmol/l in controls), as was vasopressin (7·2 ± 1·5 vs 19·7 ± 4·5 pmol/l in controls). Intravenous infusion of oxytocin (2–5 mU/min for 144·3 ± 8·2 min; total infused 448·5 ± 61·9 mU) after i.c.v. morphine re-started parturition; all pups were born to these rats (mean time to pup 6, 110·3 ± 12·7 min) before the i.v. vehicle-infused rats given i.c.v. morphine re-started (mean time to pup 6, 406·3±125·2 min).

It is concluded that morphine given during parturition acts centrally through opioid receptors to inhibit oxytocin secretion, and impairs the expression of maternal behaviour. Reversal of the effects of morphine on parturition by i.v. oxytocin demonstrates the important role of oxytocin in fetus ejection and expulsion.

Journal of Endocrinology (1989) 121, 521–536
Angiotensin II and potassium activate different calcium entry mechanisms in rat adrenal glomerulosa cells
Authors: Spät A. , Balla I. , Balla T. , Cragoe E. J. , Hajnóczky Gy. , Hunyady L.
Published: December 2008

Initial 45Ca uptake was measured in isolated rat glomerulosa cells. A small reduction in membrane potential produced by increasing the K+ concentration from 2 to 3·6 mmol/l stimulated 45Ca uptake by about 35%, while a bigger depolarization induced by 18·5 mmol K+/l increased the uptake by about 100%. Since Ca2+ influx was already activated at a calculated membrane potential below −70 mV, and was found to be sensitive to the dihydropyridine antagonist nifedipine (1 μmol/l), but insensitive to nickel ions (100 μmol/l), it does not meet the criteria established for T- or L-type voltage-dependent Ca2+ channels. Exposure of glomerulosa cells to angiotensin II (AII) for 10 min also enhanced the rate of 45Ca influx. The effect of AII was not sensitive to 1 μmol nifedipine/l, but was strongly inhibited by 5-(N-4-chlorobenzyl)-N-(2′,4′-dimethyl)benzamil (CBDMB, 30 μmol/l), an inhibitor of the Na+/Ca2+ antiporter. These observations suggest that during the sustained phase of stimulation with AII, a CBDMB-sensitive mechanism, rather than dihydropyridine-sensitive calcium channels, is involved in Ca2+ uptake in rat glomerulosa cells. The bulk Ca2+ influx did not correlate with aldosterone production; however, the maintained activity of different Ca2+ entry mechanisms seems to be essential for AII-induced aldosterone production.

Journal of Endocrinology (1989) 122, 361–370
The effects of knife cuts in the sub-paraventricular zone of the female rat hypothalamus on oestrogen-induced diurnal surges of plasma prolactin and LH, and circadian wheel-running activity
Authors: Watts A. G. , Sheward W. J. , Whale D. , Fink G.
Published: December 2008

To investigate the role of suprachiasmatic efferent connections in the expression of diurnal hormone rhythms, the efferent pathway from the suprachiasmatic nucleus (the putative circadian generator in the rat) to the sub-paraventricular zone (the main terminal area of suprachiasmatic efferents) was disrupted using bilateral horizontal knife cuts in ovariectomized oestrogen-treated rats. The position of the knife cut was assessed by observing its effect on vasoactive intestinal polypeptide immunoreactivity (a marker for suprachiasmatic efferents into the sub-paraventricular zone). The size of both the diurnal plasma LH and prolactin surges was markedly and consistently reduced over the 3-week period following the lesion in animals with a total deafferentation of the sub-paraventricular zone, compared with sham-operated animals or lesioned animals with an intact sub-paraventricular zone. When lesioned animals were grouped according to the presence or absence of damage to the preoptic area, no significant differences were found in the sizes of the plasma hormone surges. When similar knife cuts were given to animals whose activity cycles were observed, no significant effects were noted in the ability of the animals to synchronize to a light/dark regime or to free-run in constant light conditions. These results suggest that the suprachiasmatic nucleus influences the diurnal surges of plasma LH and prolactin in oestrogen-treated ovariectomized rats, initially by an interaction with the sub-paraventricular zone, and not by a direct influence on gonadotrophin-releasing hormone neurones or other more rostral structures.

Journal of Endocrinology (1989) 122, 593–604
Testosterone treatment restores reduced vasopressin-binding sites in the kidney of the ageing rat
Authors: Herzberg N. H. , Goudsmit E. , Kruisbrink J. , Boer G. J.
Published: December 2008

Young, middle-aged and aged rats received s.c. testosterone implants for 50–52 days in order to investigate whether supplementation of testosterone in aged rats could normalize the reported reduction of kidney arginine vasopressin (AVP)-binding sites and increase the plasma concentration of AVP. Receptor number, which was measured by means of a membrane-binding assay with [3H]AVP as ligand, was below the detection level in the untreated aged rat. Following testosterone treatment, no effects were seen in the youngest groups, but in the aged group AVP receptors became clearly detectable, albeit with a lower affinity. A remarkable observation was the increase in affinity for renal AVP binding in the middle-aged compared with the young rat. Plasma levels of AVP in control aged rats tended to be higher. Such a tendency was completely absent in the testosterone-treated aged rats. Possible mechanisms underlying the restoration of reduced AVP-binding sites in the kidney of the aged rat by testosterone treatment are discussed.

Journal of Endocrinology (1989) 123, 59–63
The International Standard for Pituitary FSH: Collaborative study of the Standard and of four other purified human FSH preparations of differing molecular composition by bioassays, receptor assays and different immunoassay systems
Authors: Storring P. L. , R. E. Gaines Das
Published: December 2008

The International Standard for Pituitary FSH (IS; in ampoules coded 83/575) was assayed in terms of the Second International Reference Preparation of Human Pituitary FSH and LH for Bioassay (IRP 78/549) by 27 laboratories in 13 countries using bioassays, receptor assays and immunoassays. Estimates of the FSH content of the IS by in-vivo bioassay were homogeneous both within and between laboratories and gave a combined geometric mean (with 95% fiducial limits) of 79·9 (74·6–85·4) i.u./ampoule. Estimates by different in-vitro bioassays and receptor assays were also homogeneous between assays and laboratories, and gave a combined geometric mean (with 95% fiducial limits) of 31·2 (28·8–33·9) i.u./ampoule. However, estimates by the 19 different immunoassay systems were heterogeneous and varied between 5 and 31 i.u./ampoule.

The material in ampoules coded 83/575 was established by the World Health Organization as the International Standard for Pituitary FSH. It was assigned a unitage of 80 i.u./ampoule on the basis of its calibration by in-vivo bioassay, because this assay best identifies and defines the hormone. However, the introduction of the new IS will necessitate the recalibration of immunoassay kits.

FSH 84/530, prepared in the same way as the IS from the same FSH preparation, did not differ significantly from the IS in any of the assay systems studied and appeared to be equally suitable as a standard.

Four highly purified preparations of human FSH (FSH A–D), differing in their isoform compositions and in their in-vivo: in-vitro bioactivity ratios, were also studied. The ranking order of the specific activities of FSH A–D by in-vitro bioassays paralleled their order by receptor assays and the order of their content of FSH isoforms with isoelectric points > 4·5. (Potency estimates of FSH B and C in terms of the IS were greater by receptor assay than by in-vitro bioassay.) The overall ranking order of the specific activities of FSH A–D by immunoassays was different. Contrary to expectation, estimates in terms of the IS of specific activities by immunoassay differed more between preparations than those by in-vitro bioassay or receptor assay.

Differences in specificity between immunoassay systems were demonstrated not only in the calibration of the IS in terms of the crude FSH of IRP 78/549 but also in the comparisons of the highly purified FSH in the IS and FSH A–D. The differences in the immunoreactivities and bioactivities of FSH preparations differing in their isoform compositions greatly complicate the standardization of assays for FSH.

Journal of Endocrinology (1989) 123, 275–293
Short- and long-term effects of an LHRH antagonist given during the prepubertal period on follicle dynamics in the rat
Authors: Meijs-Roelofs H. M. A. , van Cappellen W. A. , van Leeuwen E. C. M. , Kramer P.
Published: December 2008

The effects of the suppression of the high gonadotrophin concentrations normally present by the end of the second week of life on ovarian follicle dynamics were studied in immature rats. Gonadotrophins were suppressed by treatment with an LHRH antagonist (LHRH-A; Org. 30276) on days 6, 9, 12 and 15, and the total population of ovarian follicles was studied at 15 and 28 days, on the day of first oestrus and on the day of oestrus at or following 90 and 300 days of age. Primordial follicles were counted and growing follicles were counted and measured. In rats treated with LHRH-A, follicle recruitment into the growing pool was clearly diminished; the number of growing follicles was significantly (P<0·01) lower up to the day of first oestrus and the pool of primordial follicles was significantly (P<0·05) larger at 15 and 28 days. Ovarian weights were significantly lower in rats treated with LHRH-A until at least 90 days of age. However, on the day of oestrus at or after 90 and 300 days of age, there were no differences in either the pool of primordial follicles or the pool of growing follicles between rats treated with LHRH-A and control rats. There was also no difference between groups in the number of fresh corpora lutea at these ages. It was concluded that the early peak in gonadotrophin concentrations in immature rats causes substantial recruitment of follicles into the growing pool. Thus, the number of follicles entering the growing pool is not solely dependent upon the size of the pool of primordial follicles but is clearly influenced by the level of circulating gonadotrophins.

In contrast, the large gonadotrophic stimulation that normally takes place during the second and third week of life is neither a prerequisite for functional sexual maturation nor for later cyclic function. Shortly before the time of first ovulation a tight control of follicle dynamics is established which is largely independent of previous gonadotrophin concentrations and follicle dynamics.

Journal of Endocrinology (1990) 124, 247–253
Oxytocin receptors in the oviduct during the oestrous cycle of the ewe
Authors: Ayad V. J. , McGoff S. A. , Wathes D. C.
Published: December 2008

The presence of oxytocin receptors in ovine oviduct has been investigated. High-affinity binding sites for [3H]oxytocin were detected in crude membrane fractions prepared from the oviducts of ewes killed during the oestrous period. The dissociation constant calculated for these sites in competition studies was 1·7 nmol/l. Similar dissociation constants were calculated for [Arg8]-vasopressin and the oxytocin-specific agonists [Gly7]-oxytocin and [Thr4, Gly7]-oxytocin, indicating that these sites represent oxytocin receptors. At least one additional site of lower affinity and undetermined identity was present.

The relative concentration of oxytocin-binding sites in preparations of oviduct membranes were estimated in ewes killed at different stages of the oestrous cycle using a single concentration of [3H]oxytocin. Binding was low during the luteal phase of the cycle but increased to a maximum at oestrus (77·7 fmol/mg protein). Binding fell after ovulation, reaching what appeared to be basal concentrations by the early luteal stage of the cycle. Binding to oviductal membranes from prepubertal, anoestrous and pregnant ewes was also low, but in anoestrous animals which had been treated with progesterone and oestrogen it was similar to values measured in ewes at oestrus. These results are consistent with the existence of oviductal oxytocin receptors which are regulated by ovarian steroids.

We conclude that oxytocin receptors are present in the oviduct of the ewe around the time of ovulation. The significance of oxytocin to events taking place in the oviduct at this time remains to be determined.

Journal of Endocrinology (1990) 124, 353–359
Corticotrophin-releasing peptides in rat hypophysial portal blood after paraventricular lesions: a marked reduction in the concentration of corticotrophin-releasing factor-41, but no change in vasopressin
Authors: Antoni F. A. , Fink G. , Sheward W. J.
Published: December 2008

Previous data show that corticotrophin-releasing factor-41 (CRF-41), arginine vasopressin (AVP) and oxytocin are released into hypophysial portal blood. It has been presumed that the CRF-41 originates mainly from parvicellular neurones of the paraventricular nuclei (PVN); however, AVP and oxytocin could also be derived as a consequence of preterminal release from magnocellular projections to the neurohypophysis. The latter has been suggested to be the case for AVP as assessed by studies of the median eminence in vitro. Here we have investigated the source of CRF-41, AVP and oxytocin in hypophysial portal blood of adult male Wistar rats 8–10 days after surgical lesioning of the PVN. In PVN-lesioned animals the output of CRF-41 into hypophysial portal blood was reduced by about 90%, and that of oxytocin by about 40%: however, the output of AVP into portal blood was reduced only by about 10%. The release of AVP into portal blood increased after adrenalectomy; this increased release could be returned to normal by treatment with dexamethasone. No change of AVP release occurred after adrenalectomy in animals in which the PVN had been lesioned. These results show (i) that most of the CRF-41 released into hypophysial portal blood is derived from the PVN, (ii) that in PVN-lesioned animals AVP and oxytocin release remains at near normal or 60% of normal respectively, suggesting that a substantial amount of both neuropeptides in portal blood is derived as a consequence of preterminal release from supraoptic nuclei projections in the median eminence, and (iii) that glucocorticoid feedback inhibition of AVP release is exerted at the level of the PVN.

Journal of Endocrinology (1990) 125, 175–183
Sex differences in cytochrome P-450-dependent xenobiotic and steroid metabolism in the mature rainbow trout kidney
Authors: Andersson T.
Published: December 2008

The rainbow trout kidney during the late reproductive stages was found to exhibit a profound sex-related difference in its capacity to metabolize both xenobiotic model substrates and endogenous steroids. The cytochrome P-450 content of trunk kidney microsomes was 28-fold higher in males than in females. In trunk kidney microsomes, the dealkylation of various 7-alkoxycoumarins was 22- to 38-fold higher in males than in females, whereas ethylmorphine-N-demethylase (EMND) and 7-ethoxyresorufin-O-deethylase (EROD) activities were only slightly higher in males than in females. In contrast to the alkoxycoumarin- and EROD activities, the EMND activity showed considerable activity in the head kidney microsomes and the level was found to be higher in females than in males. Progesterone and androstenedione 16- and 6β-hydroxylase activities were present mainly in the male trunk kidney microsomes. On the contrary, the oestradiol 2-hydroxylase was distributed along the whole kidney and showed a 2·8-fold higher activity in the female head kidney than in the male head kidney. The catalytic analysis indicated a differential regulation of trout renal P-450 isoenzymes during sexual maturation. Furthermore, the data presented indicate that the high level of the hemoprotein in male trunk kidney was not a general increased level of the protein, but rather an increase of certain cytochrome P-450 isoenzymes.

Journal of Endocrinology (1990) 126, 9–16
Mutant gene-induced disorders of structure, function and thyroglobulin synthesis in congenital goitre (cog/cog) in mice
Authors: Adkison L. R. , Taylor S. , Beamer W. G.
Published: December 2008

We have investigated thyroid structure and function in mice homozygous for the chromosome 15 mutation, congenital goitre (cog). Abnormal thyroidal hypertrophy and reduced iodine uptake in cog/cog mice were observed as early as day 18 of gestation, corresponding to the onset of thyroid function. Growth continued unabated in mutants throughout the 10-month period of observation. By 2 months of age, thyroid cell hypertrophy obliterated nearly all follicular lumina in cog/cog glands and by 10 months mean mutant thyroid mass exceeded that of age-matched littermates. Twenty-fold serum concentrations of thyrotrophin were significantly increased at all ages examined. While wild type (+/+) and heterozygote (+/cog) mice are indistinguishable from each other, thyroids of homozygote mutants (cog/cog) and the +/cog type are easily discernible from thyroids of the +/+ type by microscopic and thyroglobulin (Tg) analyses.

Thyrofollicular cells of both cog/cog and +/cog genotypes contain large vesicles of accumulated, non-glycosylated proteinaceous material not observed in cells from +/+ mice. Autoradiography showed 125I was incorporated only into Tg within recognizable follicular lumina of thyroids from +/cog mice. Serum concentrations of tri-iodothyronine are depressed during development in cog/cog mice. Serum concentrations of thyroxine are depressed during postnatal development but increase progressively to normal concentrations by 10 months of age. Our analyses indicate that full size Tg is produced in thyroid cells from cog/cog mice, though in a greatly reduced quantity, and that Tgs which are several sizes smaller than normal are also produced in both homozygote and heterozygote thyroids. In addition, we observed altered electrophoretic mobilities of 19S Tg and either the absence or greatly reduced quantities of one reduced 12S Tg form. Tg mRNA is apparently normal size in the mutant. However, there is a five- to tenfold reduction in the amount of polyadenylated Tg mRNA available that correlates with the decreased amounts of full size Tg seen in the mutant. Collectively, these findings suggest that the compensatory goitre of cog/cog mice results from disordered processing of Tg mRNA transcribed from the cog mutant gene.

Journal of Endocrinology (1990) 126, 51–58
Inhibin, gonadotrophins and sex steroids in dogs with Sertoli cell tumours
Authors: Grootenhuis A. J. , van Sluijs F. J. , Klaij I. A. , Steenbergen J. , Timmerman M. A. , Bevers M. M. , Dieleman S. J. , de Jong F. H.
Published: December 2008

Inhibin bioactivity and mRNA for inhibin subunits were measured in four dog Sertoli cell tumours and in the testes of five normal control dogs. The tumours contained increased levels of inhibin (P <0·05) and mRNA for the α and βB subunits when compared with controls, whereas the mRNA for the βA subunit was not detected in tumours or control testes. The inhibin bioactivity was associated with a 32 kDa molecule in both Sertoli cell tumours and normal dog testes; no higher molecular weight forms were found after sodium dodecyl sulphate-polyacrylamide gel electrophoresis.

Peripheral levels of immunoassayable inhibin in dogs with Sertoli cell tumours were higher than those in the controls (P = 0·01), indicating that it might be possible to use this parameter as a marker for Sertoli cell tumours. Other testicular tumours, however, might also secrete immunoactive inhibin. The increased inhibin concentrations are likely to be the cause of the suppressed peripheral levels of FSH (P <0·02). However, peripheral levels of LH (P <0·02) and testosterone (P <0·01) were also suppressed in the dogs with Sertoli cell tumours, whereas the concentrations of oestradiol in the peripheral plasma of both groups did not differ. Finally, i.v. injection of the LHRH agonist buserelin caused a significant increase in LH and testosterone in the control dogs, but not in the dogs with Sertoli cell tumours.

It was concluded that secretory products from the Sertoli cell tumours suppressed pituitary gonadotrophin secretion. It is unlikely that testosterone or oestradiol play a role in this respect. FSH may be suppressed by the high levels of inhibin in tumour-bearing dogs, but it remains unclear whether inhibin or another Sertoli cell product is responsible for the unresponsiveness of the pituitary gland to LHRH and the suppression of LH.

Journal of Endocrinology (1990) 127, 235–242
Thyroid hormones during development of a marsupial, the tammar wallaby, Macropus eugenii
Authors: Janssens P. A. , Grigg J. A. , Dove H. , Hulbert A. J.
Published: December 2008

The levels of thyroid hormones in the plasma and the activities of 5′-deiodinase activity in liver and kidney were determined in the tammar wallaby, Macropus eugenii, from early pouch life to adulthood. The total concentration of plasma thyroxine (T4) was below 15 nmol/l before day 75 of pouch life, rose to about 75 nmol/l at day 160, and then decreased to about 12 nmol/l in the adult. The total concentration of plasma tri-iodothyronine (T3) was below 0·4 nmol/l before day 120, increased to 3 nmol/l by about day 220 and then decreased to 1·0 nmol/l in adults. Concentrations of free T4 and free T3 followed a similar pattern but peaked at 45 and 160 pmol/l respectively. Concentrations of reverse T3 (rT3) were extremely variable, ranging from 0 to 1 nmol/l at day 100, and from 0 to > 2 nmol/l at day 180. After about day 230, rT3 levels fell rapidly and were below 0·3 nmol/l in adults. Liver and kidney 5′-deiodinase activities, which were undetectable before day 80, reached adult levels by day 220. Half-maximal activity of both these enzymes occurred at about day 205, mid-way between the peaks of T4 and T3. These findings suggest that the systems supporting synthesis and release of hormones from the thyroid gland are probably mature by about day 160 of pouch life in the tammar, while peripheral deiodinase activity, which is a major factor in the production of T3 in the plasma, matures by about day 220. These events thus precede the development of physiological independence of the young tammar from its mother.

Journal of Endocrinology (1990) 127, 427–436
Applicability of the product isolation and the radiometric aromatase assays for the measurement of low levels of aromatase: lack of aromatase activity in the human endometrium
Authors: Prefontaine M. , Shih C. , Pan C. C. , Bhavnani B. R.
Published: December 2008

The purpose of this investigation was to assess the applicability of two well established procedures: (i) the product isolation assay and (ii) the radiometric 3H2O assay for the determination of very low levels of aromatase activity. The methods were validated and used to assess the capacity of normal and neoplastic human endometrium to synthesize oestrogens from androgens. Using the product isolation assay, various specimens (n = 27) of normal and neoplastic endometrium were incubated with [1,2,6,7-3H]testosterone either by a standard incubation procedure or by a superfusion technique. Following the incubation, carrier oestrone and oestradiol or [14C]oestrone and [14C]oestradiol were added, and the oestrogens were isolated and purified by paper chromatography and high-performance liquid chromatography. The radiochemical purity of oestrone and oestradiol was checked by the isotope dilution technique. In all samples, the 3H associated with oestrone and oestradiol failed to recrystallize as oestrone and oestradiol. No radioactivity was detectable in the oestrone and oestradiol crystals after acetylation. Similarly, 16 endometrial samples were tested for aromatase activity by the 3H2O release assay using [1β-3H]androstenedione as substrate. The results indicate that 3H2O was indeed released during these incubations, but this activity could not be inhibited by the aromatase inhibitor 4-hydroxyandrostenedione, by excess substrate or by heat inactivation of the tissue. Furthermore, the release of 3H2O from [1β-3H]androstenedione under the incubation conditions used (Dulbecco's modified Eagle's medium or RPMI-1640 containing fetal bovine serum and NADPH) also occurred in the absence of any tissue. This activity was not inhibited by 4-hydroxyandrostenedione nor by excess substrate. The results demonstrate that the human endometrium does not contain detectable levels of aromatase activity and that the radiometric assay can give rise to false-positive results if used for detection of very low levels of aromatase activity.

Journal of Endocrinology (1990) 127, 539–551
EVIDENCE FOR EXTENDED MAINTENANCE OF THE CORPUS LUTEUM BY UTERINE INFUSION OF A RECOMBINANT TROPHOBLAST α-INTERFERON (TROPHOBLASTIN) IN SHEEP
Authors: Martal J. , Degryse E. , Charpigny G. , Assal N. , Reinaud P. , Charlier M. , Gaye P. , Lecocq J.P.
Published: December 2008

Ovine trophoblastin (oTP) is a natural interferon of the class-II interferon-α subfamily. Recombinant ovine trophoblastin (r.oTP), produced by genetic engineering, was purified by anion-exchange HPLC. The product exhibited a high degree of homogeneity (>98%), and similar immunological cross reaction and antiviral activity to natural oTP. Antiluteolytic activity of r.oTP was established by intrauterine injection in two groups of cyclic recipient ewes. Control group A included 10 ewes which received sterile BSA in saline twice daily for 8 days (from day 10-12 of oestrous cycle). Experimental group B included 17 ewes which received 80 μg (4 ewes), 170 μg (8 ewes) or 340 μg (5 ewes) r.oTP daily for 8 days. Maintenance of functional corpora lutea for 1 month or more was observed in 4 out of 5 ewes which received high doses of r.oTP. These results indicate that oTP alone extends luteal secretory activity.
Progesterone and 5β-pregnanediol production by isolated fetal placental binucleate cells from sheep and goats
Authors: Wango E. O. , Heap R. B. , Wooding F. B. P.
Published: December 2008

Enzymic dispersion and density gradient separation were used for the isolation of enriched populations (60–90%) of cells from the corpus luteum, placenta and peripheral blood of pregnant sheep and goats. Analysis of the steroids produced from radioactive pregnenolone demonstrated that placental binucleate cells can produce progesterone and 5β-pregnanediol whereas white blood cells were relatively inactive. Thus, sheep binucleate cells converted pregnenolone predominantly to progesterone as did sheep luteal cells. However, goat binucleate cells produced 5β-pregnanediol as the major metabolite, which is consistent with its production in vivo during pregnancy. Production of progesterone (sheep) or 5β-pregnanediol (goat) by binucleate cells was shown to be proportional to the number and viability of the cells. In contrast with the binucleate cells there was no evidence that trophectodermal uninucleate cells play a significant role in placental progesterone or 5β-pregnanediol synthesis in either species.

Journal of Endocrinology (1991) 129, 283–289
Steroidogenesis during postnatal development in the mouse ovary
Authors: Mannan M. A. , O'Shaughnessy P. J.
Published: December 2008

In the mouse, follicular formation and development is largely postnatal. Changes in ovarian steroidogenesis during early postnatal life are likely, therefore, to reflect changes in follicular activity during early folliculogenesis. In this study, basal progesterone and androstenedione production and responsiveness to gonadotrophins, dibutyryl cyclic AMP (dbcAMP) and 22R-hydroxycholesterol have been measured following short-term in-vitro incubations of ovaries from mice aged 1, 3, 5, 7, 10 or 15 days. On the day of birth (day 1), basal and gonadotrophin-stimulated progesterone and androstenedione production were undectectable although a response to dbcAMP and a low level of cholesterol side-chain cleavage (CSCC) activity (measured using 22R-hydroxycholesterol) were present. On day 3 progesterone and androstenedione production were undetectable under all conditions. On day 5 only a low level of CSCC activity was detectable but on day 7 there was an increase in ovarian steroid production. Basal progesterone and androstenedione were detectable and LH, but not FSH, increased the production of both steroids. These changes were associated with a marked increase of more than 80-fold in CSCC activity. Basal steroid output increased from days 7 to 15 and LH continued to stimulate progesterone accumulation although no effect on androstenedione was seen. Addition of FSH had no effect on steroidogenesis on day 10 but significantly increased progesterone production on day 15. Ovaries from the mice used in these studies contained primordial follicles and stromal tissue on day 1. By day 5 primary and secondary follicles were present and the major increase in steroid production between days 5 and 7 was associated with an increase in secondary follicles and increased differentiation of the thecal tissue. These results show that there is a major increase in ovarian steroidogenesis at day 7 in the mouse and suggest that during folliculogenesis significant gonadotrophin-sensitive steroidogenesis may first be seen in the thecal tissue of the secondary follicle.

Journal of Endocrinology (1991) 130, 101–106
Platelet-activating factor stimulates the release of atrial natriuretic factor from the rat heart
Authors: Rayner T. E. , Menadue M. F. , Oliver J. R.
Published: December 2008

Atrial natriuretic factor (α-ANF(99–126); ANF) is released from atrial cells following atrial distension, myocardial infarction and periods of ischaemic or tachyarrhythmias. In this report we demonstrate that platelet-activating factor (PAF) stimulates ANF release from the isolated perfused rat heart and following i.v. injection to conscious unrestrained rats. ANF release peaked at 145% above baseline following injection of 2·5 nmol PAF into the isolated heart while administration of 2 nmol in vivo produced a 135% increase in plasma ANF levels. The PAF receptor antagonist BN52021 (10 μmol/l) attenuated this stimulated release, with the results suggesting a role for PAF in ANF secretion following release from damaged myocardium or as a humoral factor originating from the kidney.

Journal of Endocrinology (1991) 130, 281–288