bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of inhibin production by primate granulosa cells
Authors: Hillier S. G. , Wickings E. J. , Saunders P. T. K. , Dixson A. F. , Shimasaki S. , Swanston I. A. , Reichert L. E. , McNeilly A. S.
Published: December 2008

In-vitro data from experiments on rats implicate granulosa cells as primary sites of hormone-dependent ovarian inhibin biosynthesis, but no equivalent data exist for primates. We have used the common marmoset (Callithrix jacchus) to investigate inhibin biosynthesis in primate granulosa cells in vitro and to determine its relationship to preovulatory follicular development. To relate the production of immunoactive inhibin to follicular maturity, we studied primary granulosa cell cultures from follicles at progressive stages of preovulatory development. Granulosa cells from 'large' (≥2·0 mm diameter) follicles expressed high rates of inhibin production and steroidogenesis (progesterone), and were positively regulated by human (h)LH in vitro. Less mature granulosa cells from 'medium' (1·1–1·9 mm) and 'small' (≤ 1·0 mm) follicles expressed proportionately lower rates of inhibin production and steroidogenesis, but each parameter was stimulated in a dose- and time-dependent manner by hFSH in vitro. The stimulatory action of hFSH on immunoactive inhibin was augmented by the presence of testosterone or oestradiol; testosterone (but not oestradiol) also augmented the steroidogenic response to hFSH. Marmoset luteal tissue also produced inhibin in vitro and expressed an ∼1·5 kb inhibin α-subunit mRNA, confirming the corpus luteum as a source of ovarian inhibin in primates.

These results provide direct experimental evidence that primate granulosa cells produce inhibin. They suggest that production of inhibin by immature granulosa cells is initially induced by FSH and subject to modulation by follicular steroids. During advanced preovulatory development, granulosa cell inhibin production becomes directly responsive to LH, thereby indicating a role for LH in the control of peri- and postovulatory inhibin secretion by the primate ovary.

Journal of Endocrinology (1989) 123, 65–73
Changes in cytosolic 3,5,3′-tri-iodo-l-thyronine (T3) binding activity during administration of l-thyroxine to thyroidectomized rats: cytosolic T3-binding protein and its activator act as intracellular regulators for nuclear T3 binding
Authors: Nishii Y. , Hashizume K. , Ichikawa K. , Miyamoto T. , Suzuki S. , Takeda T. , Yamauchi K. , Kobayashi M. , Yamada T.
Published: December 2008

Changes in the amount of cytosolic 3,5,3′-tri-iodo-l-thyronine (T3)-binding protein (CTBP) and its activator during administration of l-thyroxine (T4) to thyroidectomized rats were investigated. Thyroidectomy decreased the amount of CTBP in the kidney, whereas the activator was not significantly modified by thyroidectomy. The activator was increased by administration of T4 to thyroidectomized rats. The amount of CTBP was also increased by administration of T4. The activator increased the maximal binding capacity (MBC) without changes in the affinity constant for T3 binding in CTBP. A T4-induced increase in MBC in cytosol inhibited nuclear T3 binding in vitro by competition of T3 binding between CTBP and the nuclear receptor.

These results suggest that thyroid hormone increases the capacity for cytosolic T3 binding through increasing the amount of CTBP and its activator, and that these increases play a role in regulating the amount of T3 that binds to its nuclear receptor.

Journal of Endocrinology (1989) 123, 99–104
Thyroid hormone affects the development of Sertoli cell function in the rat
Authors: Palmero S. , de Marchis M. , Gallo G. , Fugassa E.
Published: December 2008

The relationship between thyroid activity and Sertoli cell function has been investigated in prepubertal rats. Male 28-day-old Wistar rats were used to prepare Sertoli cells by sequential enzyme digestion of the testes. Hypothyroidism, induced by oral administration of methimazole from the day of birth, was characterized by a severe retardation of body and testis growth and a net inhibition of the increase in Sertoli cell γ-glutamyl transpeptidase (GGT) activity as well as in androgen-binding protein (ABP) and lactate production, which normally occur during postnatal development of Sertoli cells. The functional parameters of Sertoli cells from hypothyroid 28-day-old rats approximated to those of cells from euthyroid 15-day-old animals. These results are consistent with the impairment of protein synthesis in Sertoli cells from hypothyroid rats compared with controls.

Body and testis growth were improved and Sertoli cell functions were restored with 3,3′,5-tri-iodothyronine (T3) replacement therapy. An excess of T3 in the serum, induced by daily i.p. injections of T3 (100 μg/kg body wt) during the last week before the rats were killed, failed to induce changes in body and testis growth or in the activity of GGT and lactate dehydrogenase of Sertoli cells. Cells from hyperthyroid rats exhibited a specific decrease in ABP production. These results indicate that thyroid hormone is necessary for the postnatal maturation of Sertoli cell function and suggest a regulatory role of the hormone on gametogenic development in the prepubertal rat.

Journal of Endocrinology (1989) 123, 105–111
Changes in serum concentrations of ACTH, corticosterone and in growth following morning or evening injection of female rats with porcine growth hormone
Authors: Sillence M. N. , Etherton T. D.
Published: December 2008

The present study was designed to examine the effects of stress, associated with daily handling and placebo injection, on growth and adrenal activity in female rats. A second objective was to examine the effects of porcine GH (pGH) on growth and on serum concentrations of ACTH and corticosterone.

Treatments were administered in the morning (08.00 h) in semi-darkness, or in the evening (20.00 h) towards the end of the light period and were timed to coincide with reported periods of high and low adrenal sensitivity to ACTH.

Handling of and s.c. injection of saline into female rats (initial body weight 220 g) each morning for 21 days did not affect growth, food intake or organ weights. In contrast, daily handling and saline injection each evening caused a marked reduction in weight gain (25%), food intake (12%) and liver weight (8%), accompanied by a trend towards an increase in adrenal weight (11%), but no change in serum corticosterone concentrations.

In a second experiment, treatment of female rats (initial body weight 180 g) with pGH (5·6 mg/kg) daily at 08.00 h caused a significant improvement in weight gain (17%), but food intake and organ weights were unaltered. Daily injection of rats with pGH at 20.00 h caused a greater relative improvement in weight gain (45%) than did treatment at 08.00 h as the growth impairment caused by the stress of handling was counteracted. The adverse effect of evening injections of saline on food intake was also counteracted by pGH. Changes in liver and adrenal weights, however, were not attenuated by pGH treatment. Serum corticosterone concentrations were barely altered by pGH treatment, but serum ACTH concentrations were increased markedly (65–136%) by pGH in response to both morning and evening injection.

The results show that mild stress associated with daily handling and injection can have a profound effect on the growth of rats, but lend no support to the hypothesis that the growth impairment is mediated by corticosterone. Female rats handled and treated in the morning provide a good physiological growth model of a non-stressed animal, but rats treated in the evening are more responsive to the anabolic effects of pGH. It is suggested that pGH causes a reduction in adrenal sensitivity to ACTH and, in the absence of increased corticosterone output, high serum ACTH concentrations may contribute to part of the anabolic activity of pGH.

Journal of Endocrinology (1989) 123, 113–119
Production of calcitonin gene-related peptide from human cancer cells
Authors: Zaidi M. , Breimer L. H. , MacIntyre I.
Published: December 2008

Calcitonin (CT) is produced ectopically from a variety of non-thyroidal cancers. The CT genes also encode another peptide, calcitonin gene-related peptide (CGRP) which is a potent vasodilator. In the present study we have used immunochemical and chromatographic methods to demonstrate the presence and characterize the molecular forms of CGRP in cultured human cancer cells. Using two highly sensitive and specific radioimmunoassays, we have detected immunoreactive CGRP (i-CGRP) in cell extracts and cell-exposed media of cultured promyelocytic leukaemia (HL60) and bronchogenic carcinoma (BEN) cells. The mean i-CGRP content of the HL60 and BEN cell extracts was 2 and 45 pmol/g wet weight respectively. On gel filtration and high performance liquid chromatography, the immunoreactive material was found to be heterogeneous, though a major proportion co-eluted with synthetic human CGRP(1–37), suggesting structural identity with the intact CGRP molecule. Finally, we have discussed some interesting features of CT-gene peptide expression in tumour cells.

Journal of Endocrinology (1989) 123, 159–165
Episodic ovarian inhibin secretion is not due to LH pulses in anoestrous ewes
Authors: Campbell B. K. , McNeilly A. S. , Baird D. T.
Published: December 2008

In sheep, secretion of oestradiol by the ovary is stimulated by pulses of LH but the factors controlling ovarian inhibin secretion are not well understood. We have investigated the effect of a single injection of LH on the ovarian secretion of inhibin. Six anoestrous Finn–Merino ewes which had one ovary autotransplanted to a site in the neck had jugular and timed ovarian venous blood samples collected at 10-min intervals for a total of 5 h.

The secretion rates of both inhibin (1–3 ng/min) and oestradiol (0·5–8 ng/min) were similar to those observed during the breeding season indicating significant follicular development in these animals.

After injection of 2·5 μg NIH-LH-S25 intravenously the concentration of LH in plasma rose from a baseline of 1·8 ±0·1 (s.e.m.) μg/l to a peak of 3·9 ±0·3 μg/l (P<0·01). This LH pulse stimulated a corresponding increase (P<0·01) in oestradiol secretion from a basal level of 0·9±0·2 ng/min to a peak of 4·6±0·6 ng/min that occurred within 30 min of injection. Although inhibin secretion was episodic in nature, increases were not related to either exogenous or endogenous LH pulses.

We conclude that, in contrast to oestradiol, the secretion of inhibin by the ovary is not controlled acutely by changes in plasma levels of LH during anoestrus.

Journal of Endocrinology (1989) 123, 173–179
Leydig cell recovery following a second challenge with ethane-1,2-dimethanesulphonate is enhanced by short intervals between cytotoxin administration to rats
Authors: Edwards G. , Lendon R. , Morris I. D.
Published: December 2008

Ethane-1,2-dimethanesulphonate (EDS) destroys Leydig cells in the testis of the adult rat and subsequently a new population of Leydig cells develops. It has been reported that EDS is not cytocidal to the new immature Leydig cell population. In the present study, the effect of increasing the time-interval between injections of EDS on cytotoxicity to Leydig cells was examined. At time-intervals of 4–10 weeks between injections the response was similar to that seen after a single injection of EDS to the adult rat. Four days after the second injection, EDS was found to reduce substantially serum testosterone concentrations and in-vitro binding of 125I-labelled human chorionic gonadotrophin (hCG) to testicular LH receptors which can be correlated with Leydig cell destruction. However, when the interval was only 2 or 3 weeks there was no reduction in serum testosterone, and 125I-labelled hCG binding was not so markedly reduced. During days 1–6 after a second injection of EDS, administered 3 weeks after the first, there were marked reductions in serum testosterone concentrations and in 125I-labelled hCG binding to testis homogenates within 24 h. Recovery from the effects of EDS was rapid, and increased Leydig cell activity was seen from 2 to 6 days after injection. In contrast to the established changes in the adult rat, there was only a 50% reduction in the number of Leydig cells positive for 3β-hydroxysteroid dehydrogenase 2 days after the second injection of EDS, and after 6 days the number of cells had increased. These experiments show that the immature Leydig cell of the rat is sensitive to the cytotoxic effects of EDS but that the temporal changes in Leydig cell activity after EDS treatment are different in developing and mature Leydig cell populations. The data are consistent with the view that EDS is preferentially cytotoxic towards steroidogenically active Leydig cells, allowing the resident population of precursor cells to continue to respond to the prevailing homeostatic mechanisms.

Journal of Endocrinology (1989) 123, 197–203
Muscarinic effects on the hydroxy- and methoxyindole pathway in the rat pineal gland
Authors: Finocchiaro L. M. E. , Scheucher A. , Finkielman S. , Nahmod V. E. , Pirola C. J.
Published: December 2008

[3H]Quinuclidinyl benzylate ([3H]QNB)-binding sites, showing similar properties to cholinergic muscarinic receptors in other tissues, were disclosed in the rat pineal gland. Functionality of these receptors was demonstrated, as in-vitro muscarinic activation by pilocarpine increased the pineal metabolic production of the hydroxyindole derivatives 5-hydroxytryptophan and serotonin, with a slight effect on melatonin biosynthesis. Electric-field stimulation of pineal slices caused similar metabolic effects. These effects were inhibited by muscarinic blockade with atropine and enhanced by neostigmine inactivation of acetylcholinesterase. These results suggest that acetyl-choline is the neurotransmitter involved. Cholinergic activity may, therefore, regulate indole metabolism in the pineal gland.

Journal of Endocrinology (1989) 123, 205–211
Formation of releasable γ-aminobutyrate from putrescine by rat adrenal slices in vitro
Authors: Oon B. B. , Scraggs P. R. , Gillham B.
Published: December 2008

Rat adrenal gland slices, when incubated in vitro with [1,4-14C]putrescine, accumulate the radioactive diamine and convert it, in part, to a compound indistinguishable (in four separative systems) from [14C]γ-aminobutyrate (GABA). Adrenal glands taken from animals that had undergone adrenal enucleation 28 days previously, so that the cortex of the tissue had regenerated, likewise formed [14C]GABA from [1,4-14C]putrescine. Putrescine-derived GABA was released from adrenal slices in vitro by 48 mmol K+/l, the release being dependent upon the presence of Ca2+ in the incubation medium. ACTH(1–24) and 8-bromocyclic AMP both provoked a dose-related release of putrescine-derived GABA, although the dose–response curve for the latter differed somewhat from that for the release of corticosterone by this secretogogue.

The enzyme believed to be responsible for the first step in the metabolic transformation of putrescine into GABA, diamine oxidase (DAO), is present in extracts of adrenal tissue and its catalytic activity underwent a transient increase followed by a fall below resting levels upon stimulation of adrenal slices with ACTH(1–24). The conclusion that this enzyme initiates the formation of GABA by this pathway is indicated by the observation that adrenal slices pretreated with the DAO inhibitor, aminoguanidine, released significantly less [1,4-14C]putrescine-derived GABA in response to 48 mmol K+/l than did control tissues. The functional significance of these findings remains to be established.

Journal of Endocrinology (1989) 123, 227–232
Failure of N-(2,4-dinitrophenyl)-5-methoxytryptamine (a putative melatonin antagonist) and of N-(3,5-dinitrophenyl)-5-methoxytryptamine to prevent the effects of injections of melatonin in the late afternoon on testicular activity of the golden hamster
Authors: Pévet P. , Masson-Pévet M. , Chantegrel J. , Marsura A. , Luu-Duc C. , Claustrat B.
Published: December 2008

Daily injections of 10 μg melatonin in the late afternoon into male golden hamsters kept under a long photoperiod (14 h light: 10 h darkness) and at low ambient temperature 6 ± 1 °C) induced a complete gonadal atrophy after 4 weeks. When administered under the same conditions at doses of 25 μg, neither N-(3,5-dinitrophenyl)-5-methoxytryptamine or N-(2,4-dinitrophenyl)-5-methoxytryptamine, a putative melatonin antagonist termed ML-23 in the literature, showed any effect on testicular activity. Moreover, these two drugs were also unable to prevent melatonin-induced gonadal atrophy when injected 30 min before melatonin.

The results demonstrate that in the golden hamster and in the present experimental conditions, these drugs do not have the melatonin-antagonistic properties as described in the rat.

Journal of Endocrinology (1989) 123, 243–247
Interdependence of oestradiol and 5α-dihydrotestosterone in modulating LH and FSH secretion in rats
Authors: Schuiling G. A. , Moes H. , Koiter T. R.
Published: December 2008

The effects of oestradiol, 5α-dihydrotestosterone (DHT) and oestradiol plus DHT on pituitary responsiveness to LHRH were studied. Rats ovariectomized for 2 weeks were infused s.c. (by osmotic minipump) with LHRH at 250 ng/h for 6 days. Control rats received a sham s.c. pump. On day 3, silicone elastomer implants containing oestradiol or DHT were implanted s.c., and on day 6 the effects of these in-vivo treatments on pituitary LH and FSH content and on in-vitro (perifusion) LH and FSH secretion following maximal LHRH stimulation (1 μg/ml perifusion medium) were assessed.

Luteinizing hormone-releasing hormone alone decreased pituitary LH/FSH content and, in response to acute LHRH challenge in vitro, the absolute rate of LH/FSH release, but not LH/FSH release expressed as a fraction of pituitary content. Oestradiol alone increased pituitary LH/FSH content and LHRH-induced LH/FSH release in vitro, both absolutely and as a fraction of pituitary LH/FSH. Oestradiol exacerbated the decrease in pituitary LH/FSH caused by LHRH pretreatment in vivo, and decreased the absolute rate of LHRH-stimulated LH/FSH release in vitro, but increased this rate when it was expressed as a fraction of pituitary LH/FSH. In both LHRH-treated and control rats, DHT increased pituitary LH/FSH content, did not change the absolute rate of LH/FSH release in response to acute LHRH challenge in vitro, but decreased the rate of LH/FSH release expressed as a fraction of pituitary LH/FSH content. Combined pretreatment with oestradiol and DHT resulted in both control and LHRH-treated rats having pituitary contents comparable with those produced by DHT, similar fractions of pituitary LH/FSH release to those produced by oestradiol, and absolute rates of LH and FSH release following LHRH stimulation that were generally greater than those of the respective controls and those following other steroid pretreatment regimens. It is suggested that depletion of pituitary gonadotrophin stores caused by LHRH pretreatment in vivo, not desensitization, is responsible for the reduced LH/FSH release to an LHRH challenge in vitro and that, in the female, because of the presence of oestrogens, androgens do not exert a negative feedback on the pituitary gland as they do in the male, but, on the contrary, contribute to a high level of pituitary LHRH responsiveness.

Journal of Endocrinology (1989) 123, 257–262
Diminished role of LHRH in the control of gonadotroph morphology and function in the long-term castrated male rat
Authors: Almeida O. F. X. , Hassan A. H. S. , Nikolarakis K. E. , Martin G. B.
Published: December 2008

It was found in previous studies that the neurotransmitter control of the secretion of LHRH and LH differs between long-term castrated and ovariectomized rats. One interpretation of these data was that there was a reduced 'positive drive' in the male, and the question was raised 'how do the gonadotrophs of long-term castrated rats maintain a high level of LH secretion?'. In the present series of experiments, evidence for a reduced dependence of the gonadotrophs upon LHRH stimulation is provided. Although sensitivity to native LHRH was not completely lost in long-term castrated rats, two potent LHRH antagonists (d-pyroglu1,d-Phe2,d-Trp3,6)-LHRH and (N-acetyl-3,4-dehydro-Pro,p-fluoro-d-Phe2,d-Trp3,6)-LHRH, were found to inhibit LH secretion in short-term castrated and long-term ovariectomized rats, but not in long-term castrated rats. Neither blockade of axonal transport with colchicine nor immunoneutralization of LHRH with an antiserum against LHRH (both administered 48 h before blood sampling) produced reductions in serum concentrations of LH in long-term castrated rats, although these treatments significantly suppressed LH levels in short-term castrated animals. Chronic (6-day) infusions of the second LHRH antagonist (up to 450 μg/day) neither reduced LH secretion nor altered the morphology of the 'castration cells' in the pituitaries of long-term castrated rats. Chronic treatment with testosterone (15 days), however, reversed these parameters to some extent, and when the testosterone treatment was coupled with chronic infusions of the LHRH antagonist, significantly lower serum levels of LH and reductions in the size of the castration cells were observed. These data thus indicate that castration cells may function autonomously, without the need for LHRH, and that testosterone in some way restores the dependency on LHRH and/or the responsiveness to LHRH of these cells.

Journal of Endocrinology (1989) 123, 263–273
Influence of the thymus on steroidogenesis by rat ovarian cells in vitro
Authors: Aguilera G. , Romano M. C.
Published: December 2008

Thymic hormones and factors have been shown to modulate the function of other endocrine glands including the gonads. Absence of the thymus during development results in ovarian dysgenesis characterized by a decrease in the number of follicles and corpora lutea, bringing about severe changes in reproductive function.

To examine whether thymic secretions might affect ovarian activity, whole dispersed ovarian cells obtained from immature rats pretreated with pregnant mare serum gonadotrophin were exposed to a thymus fraction of approximately 28 kDa and also to the media from incubated thymuses (TIM) and the conditioned media from cultured thymic reticuloepithelial cells (TCM).

The thymic fraction caused a dose-dependent decrease in human chorionic gonadotrophin (hCG)-stimulated production of progesterone, oestradiol and testosterone, but had no effect on their synthesis in the absence of hCG. Similarly, hCG-induced production of these steroids was decreased by TIM and TCM. Progesterone secretion was the most markedly affected.

These results suggest: (1) that the thymus contains a factor with a molecular weight of approximately 28 kDa which interacts with hCG in ovarian cells, (2) that the thymus can release active substances which modify steroid secretion by the ovary in vitro and (3) that the reticuloepithelial cells of the thymus are involved in the secretion of factors which modulate the stimulation by hCG of steroidogenesis in ovarian cells.

Journal of Endocrinology (1989) 123, 367–373
Passively immunizing ewes against inhibin during the luteal phase of the oestrous cycle raises the plasma concentration of FSH
Authors: Mann G. E. , Campbell B. K. , McNeilly A. S. , Baird D. T.
Published: December 2008

Passive immunization was used to investigate the importance of inhibin in the negative feedback loop regulating the production of FSH in sheep. An antiserum raised to the 1–26 peptide fragment of the N-terminus of the α-chain of porcine inhibin was first shown to neutralize the suppressive effects of inhibin on the production of FSH by dispersed ovine pituitary cells in vitro. Groups of five mature Scottish Blackface ewes on day 8 of the luteal phase of the oestrous cycle were then injected with either 10 ml plasma from normal ewes (control) or 10 ml ovine inhibin antiserum. On day 10, luteal regression was induced by an i.m. injection of cloprostenol (100 μg), and ovulation rate determined 6 days later by laparoscopy. Peripheral plasma samples were collected throughout the experimental period.

Following treatment, there was no change in the peripheral plasma concentration of LH in either group. Following injection of the inhibin antiserum, the concentration of FSH rose significantly (P<0·001) compared with the control group. The concentration of FSH rose from 1·42 ± 0·06 to a maximum of 2·58 ± 0·23 (s.e.m.) μg/l by 5·6 ±0·9 h, this maximum lasting 9·0±1·1 h. By 32·8 ±6·9 h, the concentration of FSH had returned to pretreatment levels, while the titre of free antibody in the plasma of treated ewes was still high. In the treated ewes, there were one single and four double ovulations compared with three single and two double ovulations in the control group, indicating that the inhibin immunization may have resulted in an increase in ovulation rate.

We conclude that the marked rise in the plasma concentration of FSH following injection of inhibin antiserum provides strong evidence that inhibin is an important factor in the regulation of FSH production by the pituitary gland at this time.

Journal of Endocrinology (1989) 123, 383–391
Activation of pituitary-adrenal function in fetal sheep by corticotrophin-releasing factor and arginine vasopressin
Authors: Brooks A. N. , White A.
Published: December 2008

In sheep, birth is preceded by an increase in fetal plasma concentrations of ACTH and cortisol. Activation of the fetal pituitary-adrenal axis is pivotal to the onset of parturition in this species and may be regulated, at least in part, by corticotrophin-releasing factor (CRF). Pulsed administration of CRF has been shown to activate the fetal pituitary-adrenal axis in immature fetal sheep. However, pituitary ACTH responsiveness declined after continued administration of CRF, as a result of increasing negative feedback effects of increased concentrations of endogenous cortisol. To test the hypothesis that arginine vasopressin (AVP) is required, in addition to CRF, to produce the necessary trophic stimulus to the pituitary-adrenal axis, we administered saline, CRF (1 μg), AVP (200 ng) or CRF plus AVP as pulses every 4 h for 7 days to fetal sheep beginning at days 117–120 of pregnancy (term =145 days). Pituitary-adrenal responses were assessed by measuring plasma concentrations of immunoreactive (ir) ACTH and cortisol in response to one of the pulses on each of the 7 days of treatment.

On day 1, CRF and AVP significantly increased plasma concentrations of ir-ACTH and there was a synergistic interaction when the two peptides were given together (P<0·05). However, as pulsed treatment continued there was a decline in the pituitary ir-ACTH response to all treatments (P<0·05). This decline in pituitary response occurred over a much longer period of time when CRF and AVP were given together when compared with the two peptides given separately. In contrast, the cortisol response to endogenously released ir-ACTH after administration of CRF, AVP or CRF plus AVP was small on day 1 but gradually increased as treatment progressed. This was particularly apparent when the two peptides were given together. A significant inverse correlation (r = 0·781, P<0·01) between basal cortisol concentrations and the ir-ACTH response to CRF plus AVP was observed over the 7 days of treatment. Premature delivery was not induced by any of the treatments despite significant increases in fetal adrenal weight. Furthermore, there were no changes in the circulating maternal plasma concentrations of progesterone or oestrone during the 7 days of the experiment.

We conclude that combination of CRF and AVP administered as pulses to immature fetal sheep results in a greater degree of pituitary-adrenal activation when compared with the two peptides given independently. However, even after this combined treatment regimen pituitary responsiveness eventually declines, an effect which may be due to increased negative feedback effects of increased endogenous cortisol.

Journal of Endocrinology (1990) 124, 27–35
Metabolic responses to euglycaemic hyperinsulinaemia in lactating and non-lactating sheep in vivo
Authors: Faulkner A. , Pollock H. T.
Published: December 2008

Glucose utilization and production and changes in concentrations of plasma metabolites were studied in lactating and non-lactating sheep in response to three levels of insulin infusion whilst maintaining euglycaemia. Glucose utilization and production responded to insulin infusion similarly in both lactating and non-lactating ewes but, as circulating concentrations of insulin were lower in lactating animals, these parameters appeared more sensitive to plasma concentrations of insulin in lactating sheep. Changes in plasma concentrations of glycerol and free fatty acids during lactation indicated reduced sensitivity to insulin in adipose tissue and changes in plasma concentrations of amino acids were also less during lactation, suggesting reduced sensitivity of protein synthesis to insulin. Changes in plasma concentrations of urea and β-hydroxybutyrate during lactation were similar to those in non-lactating animals, indicating similar insulin sensitivity of hepatic metabolism. It is concluded that during lactation ovine adipose tissue and muscle are more resistant to increased concentrations of insulin but that the sensitivity of the sheep liver is unchanged or increased. The rate of removal of insulin from the circulation was higher in lactating animals.

Journal of Endocrinology (1990) 124, 59–66
A central action of α-melanocyte-stimulating hormone on serum levels of LH and prolactin in rats
Authors: Scimonelli T. , Celis M. E.
Published: December 2008

We have investigated the effect of administration of α-MSH into the median eminence (ME) of rats on the release of LH and prolactin.

Continuous infusion of α-MSH (0·5 μg/h) into the ME from the afternoon of the second day of dioestrus and over the 24 h of pro-oestrus inhibited the preovulatory LH and prolactin surge and the occurrence of ovulation. This inhibitory effect on LH and prolactin release was also observed in chronically ovariectomized rats given a single injection of α-MSH (1 μg/μl per rat) into the ME (blood samples were collected 0,20,60,90,105 and 120 min after injection).

The intraperitoneal injection of the dopamine receptor blocker, haloperidol (2 mg/kg), 30 min before the injection of α-MSH into the ME prevented the inhibitory effect of α-MSH on the release of LH and prolactin.

These results suggest that hypothalamic α-MSH might be involved in the regulation of LH and prolactin release via the tuberoinfundibular dopaminergic system and that this system also modifies the serum concentrations of α-MSH.

Journal of Endocrinology (1990) 124, 127–132
Release of oxytocin but not corticotrophin-releasing factor-41 into rat hypophysial portal vessel blood can be made opiate dependent
Authors: Sheward W. J. , Coombes J. E. , Bicknell R. J. , Fink G. , Russell J. A.
Published: December 2008

The effects of morphine dependence and abrupt opiate withdrawal on the release of oxytocin and corticotrophin-releasing factor-41 (CRF-41) into hypophysial portal vessel blood in rats anaesthetized with urethane were investigated. Adult female Sprague–Dawley rats were made dependent upon morphine by intracerebroventricular infusion of morphine for 5 days; abrupt opiate withdrawal was induced by injection of the opiate antagonist naloxone. The basal concentrations of oxytocin in portal or peripheral plasma from morphine-dependent rats did not differ significantly from those in control, vehicle-infused rats. In rats in which the pituitary gland was not removed after stalk section, the i.v. injection of naloxone hydrochloride (5 mg/kg) resulted in a large and sustained increase in the concentration of oxytocin in both portal and peripheral plasma in control and morphine-dependent rats. The i.v. injection of naloxone resulted in a threefold increase in the secretion of oxytocin into portal blood in acutely hypophysectomized rats infused with morphine, but did not alter oxytocin secretion in vehicle-infused hypophysectomized rats. The concentration of oxytocin in peripheral plasma in both vehicle- and morphine-infused hypophysectomized rats was at the limit of detection of the assay and was unchanged by the administration of naloxone. There were no significant differences in the secretion of CRF-41 into portal blood in vehicle- or morphine-infused hypophysectomized rats either before or after the administration of naloxone. These data show that, as for oxytocin release from the neurohypophysis into the systemic circulation, the mechanisms which regulate oxytocin release into the portal vessel blood can also be made morphine dependent. The lack of effect of morphine or naloxone on the release of CRF-41 or other stress neurohormones suggests that the effect of opiate dependence and withdrawal is selective for oxytocin and is not simply a non-specific response to 'stress'.

Journal of Endocrinology (1990) 124, 141–150
Characterization of a tissue kallikrein in human prolactin-secreting adenomas
Authors: Jones T. H. , Figueroa C. D. , Smith C. , Cullen D. R. , Bhoola K. D.
Published: December 2008

Immunoreactive tissue kallikrein was co-localized with prolactin in all the eleven prolactin-secreting adenomas of the human anterior pituitary gland examined in this study. The intracellular distribution of immunoreactivity in the prolactin-secreting cells suggests that tissue kallikrein is located within the Golgi complex of these cells. Both the intracellular hormone-processing action and the kininogenase activity of tissue kallikrein may be of functional importance in human prolactinomas.

Journal of Endocrinology (1990) 124, 327–331
An antioxidant drug, silibinin, modulates steroid secretion in human pathological adrenocortical cells
Authors: Rácz K. , Fehér J. , Csomós G. , Varga I. , Kiss R. , Gláz E.
Published: December 2008

Because human adrenocortical cells from different adrenal disorders exhibit pathologically altered corticosteroid synthesis, and free radical mechanisms may induce pathological changes in the activities of corticosteroid biosynthetic enzymes (cytochrome P-450), we examined the effect of an antioxidant, silibinin, on basal and ACTH-stimulated secretion of several corticosteroids in isolated adrenal cells from an aldosterone-producing adenoma, atrophied adrenal tissues surrounding the adenoma, and hyperplastic adrenals from Cushing's syndrome. In the presence of a high concentration (100 μmol/l) of silibinin, variably diminished secretion of basal aldosterone, corticosterone, cortisol, 18-OH-corticosterone and 11-deoxycorticosterone was found. In contrast, the addition of 0·01 μmol silibinin/l, which failed to produce a clear effect on basal corticosteroid secretion, resulted in a potentiation of ACTH-stimulated secretion of several corticosteroids in the adenomatous and hyperplastic adrenocortical cells. These results suggest that the dose-dependent dual effect of silibinin on corticosteroid secretion may be attributed to corresponding changes in the activities of cytochrome P-450 enzymes, and that stimulation of ACTH-induced corticosteroidogenesis by silibinin is presumably due to the antioxidant property of the drug.

Journal of Endocrinology (1990) 124, 341–345
Growth hormone secretion in the guinea-pig
Authors: Gabrielsson B. , Fairhall K. M. , Robinson I. C. A. F.
Published: December 2008

The guinea-pig is unusual in that it continues to grow at a normal rate after hypophysectomy. Although its pituitary gland appears to contain a GH, this has not been isolated or characterized, and nothing is known about its secretion or physiological control. We have identified guinea-pig GH, established a sensitive heterologous radioimmunoassay and adapted our automatic blood microsampling method to study spontaneous GH secretion in this species. In male guinea-pigs, GH is released in an episodic pattern, reminiscent of the rat. Large multicomponent pulses of GH secretion occur every 3–4 h between periods of low or undetectable GH release, whereas most females showed a more uniform pulsatile pattern with pulses every 1–2 h. GH was released in response to GH-releasing factor (GRF) injections (2, 10 or 20 μg [Nle27]-GRF(1–29)NH2) in a dose-dependent fashion, and i.v. infusion of somatostatin (50 μg/h) blocked spontaneous GH pulses, eliciting a rebound release (from 2·0±0·8 (s.e.m.) to 36±17 μg/l 30 min after stopping the infusion). Infusions of a GH-releasing hexapeptide (100 or 400 μg/h for 4 h) also released GH.

These results provide the first description of the pattern of GH release in the guinea-pig, and suggest that the striking episodic pattern is controlled by the same hypothalamic peptides that regulate GH in other species. Since the guinea-pig grows well in the absence of GH, this species may use GH for its metabolic, rather than growth-promoting actions. The guinea-pig may well prove a useful model, now that methods are available for studying its endogenous GH secretion.

Journal of Endocrinology (1990) 124, 371–380
Long-term reductions in GH, insulin-like growth factor-I and body weight gain in rats treated neonatally with antibodies to rat GH
Authors: Gardner M. J. , Flint D. J.
Published: December 2008

Treatment of neonatal rats on days 2–5 with antibodies against rat GH (rGH) markedly reduced body weight gain and serum concentrations of insulin-like growth factor-I for 6–8 weeks in both females and males, after which weight gain normalized without evidence of catch-up growth. There were no significant effects on serum prolactin, tri-iodothyronine or corticosterone. Testis and ovarian weights were reduced, although only in proportion to body size. In females, but not males, the treated rats, though lighter, had increased fat deposition in the parametrial depot. Pituitary weight was considerably reduced over 100 days later, as was the pituitary content of GH, but not prolactin. The response to GH-releasing factor of both male and female rats was also greatly reduced at this time. Taken together with the fact that these rGH antibodies can bind directly to somatotrophs, we propose that the long-term effects of the antibodies are induced by specific somatotroph destruction.

Journal of Endocrinology (1990) 124, 381–386
Starvation decreases insulin secretion, prostaglandin E2 production and phospholipase A2 activity in rat pancreatic islets
Authors: Tadayyon M. , Bonney R. C. , Green I. C.
Published: December 2008

Pancreatic islets, isolated from rats starved for 48 h, secreted significantly less insulin in the presence of 2 mmol glucose/l than islets of fed controls. In contrast, the insulin secretory response of islets from fed and starved rats to a challenge of 20 mmol glucose/l was similar. Concentrations of prostaglandin E2 (PGE2) in islets from starved rats incubated with 2 mmol glucose/l were significantly lower compared with those in control islets obtained from fed animals. Although glucose (20 mmol/l) stimulated PGE2 production in islets from starved and fed rats by 2·7- and 1·6-fold respectively, the concentrations achieved were the same as a consequence of the different prestimulated concentrations. Incubation with [14C]arachidonic acid of sonicated islet preparations from fed rats and separation of metabolites generated by high-pressure liquid chromatography, indicated the biosynthesis of a number of cyclo-oxygenase- and lipoxygenase-derived compounds, including 6-keto-PGF1α, PGF2α, PGE2 and 12-hydroxyeicosatetraenoic acid. Metabolism of arachidonic acid to cyclo-oxygenase-derived compounds occurred with the same efficiency, but production of lipoxygenase-derived compounds was reduced by 50% in sonicated islets from starved compared with fed rats. Activity of phospholipase A2 of islets from starved rats was significantly less than that measured in islets from fed rats, although the degree of stimulation by 20 mmol glucose/l was the same in both types of islet. These alterations in the phospholipase A2/arachidonic acid cascade may contribute to the diminished insulin secretory response of islets from starved rats to relatively low concentrations of glucose.

Journal of Endocrinology (1990) 124, 455–461
Bovine atrial natriuretic peptide in heart failure
Authors: Takemura N. , Koyama H. , Sako T. , Ando K. , Motoyoshi S. , Marumo F.
Published: December 2008

The present study describes the concentration and molecular form of atrial natriuretic peptide (ANP) in Holstein dairy cattle with mild (bacterial endocarditis; BEC) or severe (dilated cardiomyopathy; DCM) heart failure. Significant increases in plasma concentration of ANP were observed in cattle with DCM (73·3 ± 16·02 pmol/l, n=4, P<0·01) and BEC (20·6± 3·45 pmol/l, n=7, P<0·05), when compared with those in control cattle (14·5± 1·84 pmol/l, n= 12). The concentration of ANP in cattle with DCM was significantly (P<0·01) higher compared with that in cattle with BEC. Plasma concentration of ANP correlated significantly with right atrial pressure (r =0·95, P<0·01) and left ventricular end-diastolic pressure (r= 0·84, P<0·01). Gel-permeation chromatography of ANP in plasma and the right atrium from control and cattle with BEC revealed a single peak corresponding to the elution position of authentic human ANP(99–126) in plasma, and two peaks corresponding to those of authentic human ANP(99–126) and pro-ANP in the atrial extract. In cattle with DCM, however, peaks corresponding to the elution positions of authentic human β-ANP and/or pro-ANP were detected in addition to the peak corresponding to ANP(99–126). The content of ANP in the right atrium of cattle with DCM was significantly (P<0·05) increased compared with that in control cattle and those with BEC. The present study therefore suggests that the synthesis and secretion of ANP might be stimulated by atrial distention induced by increased atrial pressure. This suggestion is supported by the fact that the middle molecular weight form of ANP, possibly corresponding to human β-ANP, was detected in both the plasma and atria of the cattle with severe heart failure.

Journal of Endocrinology (1990) 124, 463–467
Gonadotrophin-binding components in porcine follicular fluid
Authors: Yarney T. A. , Sairam M. R. , Bhargavi G. N. , Downey B. R. , Srikandakumar A.
Published: December 2008

The follicular fluid is an important milieu for the growing and maturing oocyte and granulosa cells. In this study we investigated: (1) the properties of gonadotrophin-binding sites in the supernatant fraction of porcine follicular fluid (pFF) and compared them with those of membrane-bound receptors, and (2) the relative changes that occur in pFF and granulosa cell receptor-binding activity following hormone priming of gilts. 125I-Labelled human chorionic gonadotrophin (hCG) and 125I-labelled ovine FSH (oFSH) binding to particulate and supernatant fractions of pFF were hormone-specific and saturable. The concentration of 125I-labelled hCG-binding sites was roughly 50-fold higher in particulate than in supernatant fractions of pFF. However, 30–40% of the total 125I-labelled hCG-binding activity in pFF was present in the supernatant fraction of commercial batches of pFF. 125I-Labelled oFSH binding to pFF membranes was markedly higher than to supernatant fractions. Binding of 125I-labelled hCG and 125I-labelled oFSH to granulosa cells and supernatants of pFF showed a time-dependent variation in response to hormone priming. The results suggest that gonadotrophin-binding sites in the supernatant fraction of pFF have properties similar to those of their membrane-bound counterparts. 125I-Labelled hCG-binding activity in the supernatant fraction of pFF was shown to be more stable than detergent-solubilized LH/hCG receptors, even in glycerol-preserved preparations. Based on a number of criteria, we have speculated that pFF may have components which may be similar in structure to the extracellular domain of the LH/hCG receptor.

Journal of Endocrinology (1990) 124, 485–494
Alterations of serum concentrations of thyroid hormones and sex hormone-binding globulin, nuclear binding of tri-iodothyronine and thyroid hormone-stimulated cellular uptake of oxygen and glucose in mononuclear blood cells from patients with non-thyroidal illness
Authors: Kvetny J. , Matzen L.
Published: December 2008

Nuclear tri-iodothyronine (T3) binding and thyroid hormone-stimulated oxygen consumption and glucose uptake were examined in mononuclear blood cells from patients with non-thyroidal illness (NTI) in which serum T3 was significantly (P < 0·05) depressed (0·62± 0·12 (s.d.) nmol/l) compared with healthy control subjects (1·45 ± 0·30 nmol/l). Neither serum TSH nor sex hormone-binding globulin differed from that of the control group.

Nuclear T3 binding capacity was increased (P < 0·05) in patients with NTI (10·1 ± 3·0 fmol/100 μg DNA) compared with controls (2·5 ± 0-9 fmol/100 μg DNA). Unstimulated glucose uptake was increased in cells from patients with NTI (2·03 ± 0·49 mmol/l per mg DNA per h, P < 0·01) compared with controls (1·13 ± 0·20 mmol/l per mg DNA per h). Thyroxine-stimulated glucose uptake (stimulated glucose uptake–unstimulated glucose uptake) was increased in cells from patients with NTI (2·06 ± 1·67 mmol/l per mg DNA per h, P < 0·01) compared with controls (0·26 ± 0·1 mmol/l per mg DNA per h), and T3-stimulated glucose uptake was also increased in cells from patients with NTI (1·34 ± 0·81 mmol/l per mg DNA per h, P < 0·05) compared with controls (0·24 ± 0·10 mmol/l per mg DNA per h). In contrast, neither unstimulated nor thyroid hormone-stimulated oxygen consumption differed.

We conclude that both increased nuclear T3 binding and increased thyroid hormone-induced glucose uptake may represent counter-regulatory mechanisms which tend to maintain intracellular homeostasis.

Journal of Endocrinology (1990) 124, 495–499
EFFECT OF INSULIN-LIKE GROWTH FACTOR-TYPE I (IGF-I) AND INSULIN ON THE SECRETION OF SEX HORMONE BINDING GLOBULIN AND IGF-I BINDING PROTEIN (IBP-I) BY HUMAN HEPATOMA CELLS
Authors: Singh A. , Hamilton-Fairley D. , Koistinen R. , Seppälä M. , James V.H.T. , Franks S. , Reed M.J.
Published: December 2008

Dietary factors are known to modulate concentrations of sex hormone-binding globulin (SHBG). In the present study we have investigated the possibility that insulin like growth factor-type I (IGF-I) may be an additional regulator of SHBG using cultured human hepatoma cells which secrete SHBG. The inhibitory effect of insulin on SHBG secretion by these cells was confirmed but, in addition, IGF-I was shown to inhibit SHBG secretion by about 40% at a concentration of 100 nmol/l. A similar degree of inhibition was achieved using insulin at a concentration of 10 umol/l. Insulin, but not IGF-I, was also found to inhibit the secretion of a low molecular weight IGF-binding protein (IBP-I), which is also secreted by hepatoma cells. It is concluded that IGF-I is an additional regulator of SHBG secretion by these cells and that it may be involved in regulating SHBG secretion in vivo in response to dietary factors.
OXYTOCIN BIOSYNTHESIS IN SERUM-FREE CULTURES OF HUMAN GRANULOSA CELLS
Authors: plevrakis I. , Clamagirand C. , Pontonnier G.
Published: December 2008

Human granulosa cells were collected from preovulatory follicles during follicular puncture for in-vitro fertilization. They were cultured in serum-free medium supplemented with ascorbic acid. Using a combination of high-performance liquid chromatography and radioimmunoassay, the oxytocin material present in the cell extracts and secreted into the medium was identified. When cells were deprived of ascorbate, intermediary forms resulting of the post-translational processing of pro-oxytocin/neurophysin were detected. These data demonstrate that oxytocin biosynthesis occurs in human granulosa cells.