bluuebunny/crossref_metadata_2025 huggingface dataset:
Solubilization of a large molecular weight form of the rat LHRH receptor
Authors: Ogier S.-A. , Mitchell R. , Fink G.
Published: December 2008

The LHRH receptor has been solubilized from male rat anterior pituitary glands, using the zwitterionic detergent 3-((3-cholamidopropyl)-dimethylammonio)-1-propanesulphonate in the presence of a high concentration of sodium chloride. This method gave high yields (up to > 70%) of the LHRH-binding site from the membrane preparation. Ligand binding studies using LHRH analogues were carried out to determine dissociation constants for LHRH receptors both in situ in the membrane preparation and for solubilized LHRH receptors. For all the analogues the binding characteristics were similar in both preparations, suggesting that the solubilization procedure left the LHRH receptor undenatured. Gel filtration revealed an apparent molecular weight for the LHRH receptor of 100 000–160 000, with the mean value being approximately twice that found by others using sodium dodecyl sulphate–polyacrylamide gel electrophoretic techniques. The results indicate that the LHRH receptor probably exists in gonadotroph membranes as a large complex of more than one subunit.

J. Endocr. (1987) 115, 151–159
Changes in peripheral progestagen levels in early pregnant gilts following injection of human chorionic gonadotrophin
Authors: Stone B. A. , Heap P. A. , Seamark R. F.
Published: December 2008

The capacity of human chorionic gonadotrophin (hCG) to raise plasma progestagen levels during the first 8 days of gestation in gilts was examined. The effective half-times of hCG in gilts treated with 500 and 5000 i.u. hCG were 29·1 and 26·3 h respectively (P >0·05). Neither 500 nor 5000 i.u. hCG caused rises in peripheral concentrations of progesterone or pregnenolone sulphate, and plasma pregnenolone concentrations declined (P <0·05) following hCG treatment. Apart from diminished total corpus luteal weights in gilts treated with 500 i.u. hCG (P <0·05) and lower peripheral progesterone levels in gilts treated with 5000 i.u. hCG (P <0·05), ovarian and plasma steroid characteristics of hCG-treated animals between 23 and 25 days of gestation were similar to control values. Furthermore, treatment with hCG did not affect embryo survival during the first 4 weeks of pregnancy, and plasma oestrone/oestrone sulphate levels provided no evidence for differences between control and treated animals in trophoblastic out-growth. These results challenge the rationale for the treatment of early pregnant sows with hCG in order to reduce the levels of embryonic wastage in early pregnancy.

J. Endocr. (1987) 115, 161–167
Immunohistochemical demonstration of marked changes in the LHRH system of photosensitive and photorefractory European starlings (Sturnus vulgaris)
Authors: Foster R. G. , Plowman G. , Goldsmith A. R. , Follett B. K.
Published: December 2008

Immunocytochemistry was used to determine the effects of photoperiod on the LHRH neurosecretory system in the brain of male European starlings. In this species, as in other birds, reproduction is triggered by long daylengths but continued exposure leads to photorefractoriness and to a complete shut-down of the reproductive system. These effects are thought to be mediated through changes in the secretion of LHRH. In starlings exposed to a photoperiod of 11 h light: 13 h darkness (11L: 13D) and with fully developed testes there was strong immunostaining of both LHRH perikarya (n = 522 ± 43 s.e.m.) and fibres. Photosensitive short-day (8L: 16D) starlings with undeveloped testes had an almost identical distribution of strongly immunoreactive perikarya (n = 523 ± 62) but there were fewer fibres. In the median eminence, fibre number was reduced significantly (P < 0·01) by some 30%. In long-day (18L: 6D) photorefractory starlings with fully regressed testes there was an even more obvious change in the LHRH system. Perikarya were only weakly immunoreactive and there was a significant (P < 0·01) reduction in mean diameter from 10 to 6·5 μm. In addition, there was a significant (P < 0·05) reduction in cell number (312 ± 62), although this may well result from the fact that some weakly stained cells fell below the limits of resolution and could not be counted. LHRH fibres disappeared almost entirely from the median eminence, and were not visible elsewhere in the brain. The higher neural pathways regulating photorefractoriness induced by long days are unknown but clearly both production of LHRH in the perikarya and release/storage of LHRH in the terminals is being profoundly modified.

J. Endocr. (1987) 115, 211–220
Anaesthesia with alphaxalone plus alphadolone acetate decreases serum concentrations of LH in castrated rats
Authors: Emanuele M. A. , Tentler J. , Kirsteins L. , Reda D. , Emanuele N. V. , Lawrence A. M.
Published: December 2008

Alphaxalone is considered the anaesthetic of choice in neuroendocrine reproductive studies in female rats, since it appears to have little, if any, effect on release of gonadotrophin-releasing hormone. There has been less study of the effects of this anaesthetic on the male reproductive neuroendocrine axis, however. Accordingly, the time-dependent effects of alphaxalone, as well as of urethane and ketamine, on the increased levels of LH in castrated rats were determined. Each anaesthetic was administered i.p. and each depressed LH levels significantly compared with those in castrated unanaesthetized rats killed by decapitation (controls). The effect of the anaesthetics was noted 15 min after administration and persisted at 30 and 60 min in animals anaesthetized with alphaxalone and urethane. Only in ketamine-anaesthetized animals did serum concentrations of LH finally rise to concentrations not significantly different from those in control rats. Thus alphaxalone, though useful in female neuroendocrine studies, is as profoundly disruptive as other anaesthetics on the male rat hypothalamic-pituitary reproductive unit.

J. Endocr. (1987) 115, 221–223
Evidence for an interaction of insulin and sex steroids in the regulation of vitamin D metabolism in the rat
Authors: Nyomba B. L. , Bouillon R. , De Moor P.
Published: December 2008

Vitamin D metabolites and vitamin D-binding protein (DBP) were measured in non-diabetic rats and in rats made diabetic with streptozotocin. The animals were studied in the intact state, after gonadectomy and during pregnancy. In male non-diabetic rats the serum concentrations of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) and DBP decreased after orchidectomy and were restored by treatment with testosterone. In female non-diabetic rats, these parameters increased after ovariectomy. Increased 1,25-(OH)2D3 and decreased DBP concentrations were found during pregnancy in non-diabetic rats.

After the induction of diabetes in intact rats of both sexes, the concentration of DBP decreased, but a significant decrease in the concentration of 1,25-(OH)2D3 was found in male animals only. After ovariectomy, however, 1,25-(OH)2D3 decreased also in female diabetic rats.

Both orchidectomy and insulin deficiency depressed serum concentrations of 1,25-(OH)2D3 (−22 and −45% respectively) and DBP (−14 and −29% respectively), but the effects of insulin deficiency were greater than those of androgen withdrawal. Moreover, the testosterone concentration was twofold lower in intact male diabetic rats than in non-diabetic animals. Insulin, but not testosterone treatment, however, restored DBP and 1,25-(OH)2D3 concentrations in diabetic rats, and insulin was effective in intact as well as in gonadectomized animals.

This study shows that insulin deficiency decreases the concentrations of DBP and 1,25-(OH)2D3 in the rat, and that these decreases are facilitated by androgens, but counteracted by oestrogens.

J. Endocr. (1987) 115, 295–301
Sex differences in the LH responses to chicken LHRH-I and -II in the domestic fowl
Authors: Sharp P. J. , Dunn I. C. , Talbot R. T.
Published: December 2008

Maximal incremental changes in plasma LH were compared in adult hens and cockerels after i.v. injection of chicken (c) LHRH-I (pGlu1-His2-Trp3-Ser4-Tyr5-Gly6-Leu7-Gln8-Pro9-Gly10-NH2) or cLHRH-II (pGlu1-His2-Trp3-Ser4-His5-Gly6-Trp7-Tyr8-Pro9-Gly10-NH2). The LH response to cLHRH-I and -II was more rapid and greater in cockerels than in hens. The potencies of the two decapeptides were the same in cockerels but different in hens. Relative to cLHRH-I, the potency of cLHRH-II was 0·91 (0·6– 1·2; 95% confidence limits) in cockerels and 36·5 (16·8–128·6) in hens.

The greater potency of cLHRH-II relative to cLHRH-I in the hen than in the cockerel could not be accounted for by sex differences in the half-lives of the decapeptides in the peripheral circulation. The half-lives of both decapeptides in hens and cockerels ranged between 2·42 and 3·77 min.

It is concluded that the interaction between LHRH-I and -II and the gonadotrophs is sexually differentiated in the domestic fowl.

A new homologous radioimmunoassay was established for cLH. As in other chicken LH radioimmunoassays, there was evidence of cross-reactivity with TSH.

J. Endocr. (1987) 115, 323–331
Nucleotide (cDNA) sequence encoding the horse gonadotrophin α-subunit
Authors: Stewart F. , Thomson J. A. , Leigh S. E. A. , Warwick J. M.
Published: December 2008

Several cDNA clones corresponding to mRNA for the α-subunit of the horse (Equus caballus) pituitary and placental (chorionic) gonadotrophic hormones have been isolated and sequenced. Polyadenylated mRNA was purified from horse pituitary glands (the source of FSH and LH) and horse placental tissues (the source of chorionic gonadotrophin; CG). The mRNA preparations were characterized by in-vitro translation and Northern hybridization techniques using human and ovine gonadotrophin cDNA clones as probes. Complementary DNA libraries were created from the pituitary and placental mRNAs and a human CG α-subunit probe was used to isolate several horse α-subunit cDNA clones. The α-subunit nucleotide sequence from both sources of tissue was identical, thereby indicating that in the horse (as in man) the same gonadotrophin α-subunit gene is expressed in the pituitary and placenta. Our results are consistent with transcription of a single α-subunit gene for all the glycoprotein hormones in the horse, and we suggest that the reported differences between the horse CG and FSH α-subunit amino acid sequences determined by conventional peptide sequencing methods arose due to errors in the FSH α-subunit sequence. Comparison of the deduced amino acid sequence of the horse α-subunit with that of other α-subunit sequences indicated a number of significant differences which may be related to the unusual receptor-binding properties of the equine gonadotrophins.

J. Endocr. (1987) 115, 341–346
The subfornical organ and relaxin-induced inhibition of reflex milk ejection in lactating rats
Authors: Summerlee A. J. S. , O'Byrne K. T. , Jones S. A. , Eltringham L.
Published: December 2008

Experiments were carried out on anaesthetized, lactating rats to investigate the possible role of the subfornical organ in mediating relaxin-induced inhibition of reflex milk ejection. Milk ejection was judged by the behavioural response of the sucklings and by transient rises in intramammary pressure. Radiofrequency lesions of the subfornical organ, or control lesions in adjacent areas of the cerebrum, did not affect the pattern or the magnitude of intramammary pressure changes at reflex milk ejection. Purified porcine relaxin given by either i.v. (5 μg) or intracerebroventricular (50 ng) injection suppressed reflex milk ejection in intact, sham-lesioned and control-lesioned rats, but had no effect on either the pattern or magnitude of reflex milk ejection in rats with lesions of the subfornical organ. The subfornical organ, which is situated at the interface between the blood, brain and the cerebrospinal fluid appears to mediate, at least in part, the relaxin-induced inhibition of reflex milk ejection in the rat.

J. Endocr. (1987) 115, 347–353
Effects of human prostatic mitogens on rat bone cells and fibroblasts
Authors: Koutsilieris M. , Rabbani S. A. , Goltzman D.
Published: December 2008

We examined several characteristics of the mitogenic activity of extracts of human prostatic adenocarcinoma and human benign prostatic hyperplasia in fetal rat calvarial cells, cloned rat osteosarcoma cells and rat skin fibroblasts. Prostatic moieties produced maximal stimulation of [3H]thymidine incorporation at 24 h, were mitogenic in the absence or presence of various concentrations of serum, and were active in calvarial cells enriched with osteoblasts, skin fibroblasts and the cloned rat osteosarcoma cell line UMR 108. The known growth-promoting agents insulin, insulin-like growth factor, fibroblast growth factor, platelet-derived growth factor, epidermal growth factor, interleukin-1α and β and transforming growth factor β were also mitogenic in the indicator systems employed; however, maximally stimulating effects of these peptides in cells of the osteoblast phenotype were further enhanced with prostatic material. Prostatic activity was acid-stable and could be enriched with respect to osteoblast stimulation by hydrophobic and carboxymethyl ion-exchange chromatography. The results demonstrate the presence of potent mitogenic activity in hyperplastic and malignant prostatic tissue which appears to include unique osteoblast-stimulating activity.

J. Endocr. (1987) 115, 447–454
Hydroxyindole-O-methyltransferase catalyses production of methoxyindoles in rat pineal gland dependent on the concentration of hydroxy precursors and their affinity for the enzyme
Authors: Morton D. J.
Published: December 2008

Indole metabolites were separated by thin-layer chromatography following organ culture of rat pineal glands with tritiated tryptophan. Methoxyindole production was shown to differ substantially from results obtained when pineal glands were incubated with radiolabelled serotonin. The correlation between hydroxy- and corresponding methoxyindoles was, however, remarkably similar to previous results, and indicated that in the pineal gland, it is probable that production of methoxyindoles is dependent on the concentration of the various hydroxyindoles and their relative affinities for hydroxyindole-O-methyltransferase. It is also probable that although several forms of the enzyme may exist in the pineal gland, the catalytic sites are homogeneous in their activity.

J. Endocr. (1987) 115, 455–458
Ca2+ ionophore A23187-induced rise in cytoplasmic free calcium and iodide discharge in porcine thyroid cells: measurement of cytoplasmic free calcium by aequorin
Authors: Takasu N. , Murakami M. , Nagasawa Y. , Yamada T. , Shimizu Y. , Kojima I. , Ogata E.
Published: December 2008

The cytoplasmic concentration of free calcium was measured using aequorin, a calcium-sensitive photoprotein. The Ca2+ ionophore A23187 induced a rise in cytoplasmic free calcium and iodide discharge in cultured porcine thyroid cells. The minimum dose of A23187 effecting an increase in cytoplasmic free calcium induced iodide discharge. The A23187-induced rise in cytoplasmic free calcium was followed by iodide discharge. The results indicate that A23187-induced iodide discharge is mediated by a rise in the cytoplasmic concentration of free calcium.

J. Endocr. (1987) 115, 477–480
Effects of oestradiol-17β on testicular microcirculation in rats
Authors: Widmark A. , Damber J. E. , Bergh A.
Published: December 2008

The effect of oestradiol-17β on testicular micro-circulation in intact and hypophysectomized rats was studied before and after treatment with human chorionic gonadotrophin (hCG). Treatment of intact rats with oestradiol-17β for 5 days did not influence vasomotion but decreased testicular interstitial fluid volume (IFV). Treatment of intact rats with 50 IU hCG 8 h before the experiment began induced an increase in testicular IFV, abolished vasomotion and increased the accumulation of polymorphonuclear leucocytes in the testicular venules and interstitium. These changes were unaffected by pretreatment with oestradiol-17β, despite the decreased testosterone production. However, pretreatment with oestradiol-17β potentiated the hCG-induced migration of polymorphonuclear leucocytes to the interstitium. The interstitial fluid volume and number of polymor phonuclear leucocytes in blood vessels were decreased in hypophysectomized rats, and vasomotion was abolished. Daily treatment with 5 IU hCG increased the IFV and the number of polymorphonuclear leucocytes in blood vessels, and preserved vasomotion. Treatment of hypophysectomized rats with oestradiol-17β decreased testosterone production but did not influence basal IFV, vasomotion or the changes in IFV and vasomotion induced by 5 IU hCG. The present study shows that the regulation of testicular vascular permeability and vasomotion may not be directly related to testicular steroidogenesis, and that oestrogens are probably not involved as a mediator of the hCG-induced changes in testicular microcirculation.

J. Endocr. (1987) 115, 489–495
Effects of ACTH and ACTH fragments on DNA synthesis in guinea-pig adrenal segments kept in organ culture
Authors: Wulffraat N. M. , Drexhage H. A. , Jeucken P. , van der Gaag R. D. , Wiersinga W. M.
Published: December 2008

Stimulation of adrenal DNA synthesis by ACTH(1–39) and its fragments ACTH(1–24) (Synacthen) and ACTH(18–39) was investigated. Synthesis of DNA was measured as the increase in the percentage of cells in S-phase (Feulgen densitometry) in guinea-pig adrenal explants kept in organ culture and exposed to the peptides for 5 h at 37 °C. ACTH(1–39) and its C-terminal fragment ACTH(18–39) (corticotrophin-like intermediate lobe peptide) were found to be potent stimulators of in-vitro adrenal DNA synthesis. The dose–response kinetics were biphasic and optimal responsiveness was reached in both instances at 1 fmol/1–10 pmol/l (this biological effect of ACTH(18–39) has hitherto not been described). The N-terminal fragment ACTH(1–24) gave only minimal responses. Thyrotrophin and LH, tested as controls, did not induce adrenal DNA synthesis. Epidermal growth factor was a potent stimulator of adrenal DNA synthesis in vitro.

Our data suggest a trophic action of the C-terminal part (ACTH(18–39)) of the corticotrophic molecule. Clear trophic effects were also found for the N-terminal part of the pro-opiomelanocortin molecule N-POC(1–76) (optimum 0·1 nmol/l) and N-POC(51– 62) (optimum 0·1 pmol/l). The latter observations support earlier concepts that this part of the proopiomelanocortin molecule has a stimulatory effect on adrenal DNA synthesis.

J. Endocr. (1987) 115, 505–510
COLLAGEN AND NON–COLLAGEN PROTEIN TURNOVER IN SKELETAL MUSCLE OF GROWTH HORMONE–TREATED LAMBS
Authors: Pell J. M. , Bates P. C.
Published: December 2008

Long–term administration of GH to normal, well–fed lambs caused a significant increase in net muscle growth. This could be accounted for by increased rates of muscle protein synthesis, although red and white muscles responded differently. The increased rate of protein synthesis was due to an increased protein synthetic capacity (increased muscle RNA content) but efficiency per unit of RNA also tended to increase in red muscle. For similar increases in net growth, protein turnover was increased to a much greater extent in red than in white muscle. The ratio of collagen to non–collagen protein was unaffected in both muscle types by GH treatment, even though collagen synthesis rates were significantly increased in red muscle. To date, GH is the only anabolic agent in ruminants which acts via increased rates of protein synthesis rather than by decreased rates of protein degradation.
ISOLATION, AMINO ACID SEQUENCE AND ACTION OF GUINEA-PIG ACTH ON ALDOSTERONE PRODUCTION BY GLOMERULOSA CELLS
Authors: Smith A.I. , Wallace C.A. , Moritz R.L. , Simpson R.J. , Schmauk-White L.B. , Woodcock E.A. , Funder J.W.
Published: December 2008

Though minor sequence differences between-species have been reported for adrenocorticotrophin, ACTH(1–39), the steroidogenic moiety ACTH(1–24) has appeared invariant in mammals. We here report the isolation, purification and amino acid sequencing of guinea-pig (GP) ACTH in which Pro24 is replaced by [ill] Ala24, and the demonstration that GP-ACTH stimulates aldosterone production to maximal levels well above those seen with human ACTH(1–39) or Synacthen, ACTH(1–24) amide, the synthetic ACTH fragment widely used for diagnostic and therapeutic purposes.
Granulated metrial gland cells in the non-traumatized regions of the uterus of ovariectomized mice with deciduomata maintained on progesterone
Authors: Stewart I.
Published: December 2008

A study has been made of granulated metrial gland (GMG) cells in the non-traumatized regions of the uterus of ovariectomized mice maintained on progesterone and with deciduomata in part of one uterine horn. GMG cells were found in the non-traumatized region of the uterine horns with deciduomata for at least 8 days after induction of the decidual reaction. GMG cells were not found in the contralateral horns without deciduomata. Activation of endometrial stromal cells is characterized by a high mitotic index and, in mice given colchicine, numerous stromal cells were arrested in metaphase in the non-traumatized region of the uterine horns with deciduomata for at least 3 days after induction of the deciduomata. In uterine horns without deciduomata, stromal metaphases were few in number over the same period. A correlation was therefore found between the presence of GMG cells and large numbers of stromal cells in mitosis. There was also a correlation between the absence of GMG cells and small numbers of stromal cells in mitosis. These results are compatible with the hypothesis that the differentiation and maintenance of GMG cells are under the control of endometrial stromal cells.

J. Endocr. (1988) 116, 11–15
Thyrotrophin and cyclic AMP regulation of thyroglobulin gene expression in cultured porcine thyroid cells
Authors: Chabaud O. , Chambard M. , Gaudry N. , Mauchamp J.
Published: December 2008

The effects of thyrotrophin, cholera toxin and 8-chloro-cyclic AMP on thyroglobulin gene expression in cultured porcine thyroid cells were compared. Cells organized either into monolayers in culture chambers with porous bases or into inside-out follicles in suspension were used. Thyroglobulin mRNA content was measured by dot-blot hybridization, and thyroglobulin synthesis rate was determined by immunoprecipitation of [35S]thyroglobulin after 2 h labelling with [35S]methionine. Cholera toxin and 8-chlorocyclic AMP increased the thyroglobulin mRNA content and thyroglobulin synthesis rate in the same ratio (∼3) as did thyrotrophin, showing that cyclic AMP mediates the effect of thyrotrophin on thyroglobulin gene expression. The culture chamber system provides for contact of the effectors with either the apical or the basolateral membrane.

The addition of 0·02–0·1 mU thyrotrophin/ml on the basolateral side of the cell layer gave a maximal response whereas this response was not reached on the apical side even with the addition of 5 mU/ml. In contrast, cholera toxin and 8-chloro-cyclic AMP stimulated thyroid cells equally on both sides.

J. Endocr. (1988) 116, 25–33
Molecular forms of growth hormone in the chicken pituitary gland
Authors: Houston B. , Goddard C.
Published: December 2008

Different forms of GH present in freshly prepared homogenates of chicken pituitary were analysed by high-performance gel permeation chromatography and by immunoblotting following sodium dodecylsulphate polyacrylamide gel electrophoresis, non-denaturing polyacrylamide gel electrophoresis and isoelectric focussing. Chicken GH was found to occur mainly in a monomeric form with a relative molecular mass of 23 500 together with small amounts of interchain disulphide-linked oligomers. No evidence was obtained for proteolytically modified forms of GH nor for a form analogous to the 20K variant of human GH. Isoelectric focussing resolved ten distinct charge variants of chicken GH with isoelectric points between 8·45 and 6·0. The predominant charge variant (pI = 7·85) was present in pituitaries of birds of both sexes at all ages examined (3–114 days) whereas the more acidic forms were not apparent until after day 13. These findings indicate that the chicken pituitary contains different forms of GH, some of which may be developmentally regulated.

J. Endocr. (1988) 116, 35–41
Reduced oxytocin response to osmotic stimulus and immobilization stress in lactating rats
Authors: Higuchi T. , Honda K. , Takano S. , Negoro H.
Published: December 2008

The release of oxytocin in response to an osmotic stimulus and immobilization stress was compared in lactating rats 8–12 days after delivery and in non-lactating rats. Intravenous injection of hypertonic saline or immobilization stress induced an increase in blood oxytocin levels in both lactating and non-lactating rats, but the increment in the former was significantly lower than that in the latter. The lower responsiveness of oxytocin release to stress in lactating rats was not altered by ovariectomy 2 days after parturition. Oxytocin release induced by electrical stimulation of the anteroventral third ventricle (an osmoreceptive area), paraventricular nucleus and neurohypophysis was significantly lower, to a similar extent, in lactating rats compared with non-lactating rats. These findings indicate that the structural reorganization reported in the hypothalamo-neurohypophysial system may not function to facilitate release of oxytocin in response to stress and osmotic stimulus in lactating rats. The reduced responsiveness of the release of oxytocin is independent of the influence of ovarian hormones, and may be due to the low ability of the oxytocin neurone itself to release oxytocin, and/or due to the activated inhibitory influence on the oxytocin neurone in the lactating rat.

J. Endocr. (1988) 116, 225–230
Biophysical characteristics of oxytocin secretory granules isolated from ovine corpora lutea
Authors: Rice G. E.
Published: December 2008

Luteal oxytocin-containing secretory granules have been isolated and characterized in terms of their physicochemical parameters. The isopynic sedimentation density (1·03 ±0·003 g/ml) and sedimentation coefficient (1670 S, 0·32 mol sucrose/l, 4 °C) of these granules have been estimated. Based upon these estimates, the average vesicle diameter (258 ± 17 nm) and vesicle weight (9·92 ±0·67 fg/vesicle) were calculated. The exchangeable water content (58·2%) of these granules was determined using density gradients prepared with deuterium oxide. Luteal oxytocin-containing granules displayed similar physicochemical characteristics to those reported for neurohypophysial peptide-containing granules, with the exception of particle size. Luteal granules were 1·3 times greater in diameter than neurohypophysial granules.

J. Endocr. (1988) 116, 267–272
Potentiation of lactation-induced oxytocin secretion by intracerebroventricular oxytocin in the conscious goat
Authors: Seckl J. R. , Lightman S. L.
Published: December 2008

The release of oxytocin into the cerebrospinal fluid (CSF) and plasma of lactating goats was studied following implantation of cisternal and lateral ventricular cannulae. Hand milking was associated with a significant increase in plasma concentrations of oxytocin, but no change in plasma concentrations of vasopressin or CSF concentrations of oxytocin. Intracerebroventricular (i.c.v.) infusion of oxytocin itself (1 pmol/min for 60 min) had no effect on basal plasma levels of oxytocin. It did, however, markedly potentiate the milking-induced increase in plasma oxytocin above the levels achieved during i.c.v. infusion of artificial CSF alone. In the goat, therefore, milking results in a selective release of oxytocin into the plasma, and this release can be potentiated by the presence of increased concentrations of oxytocin in the CSF.

J. Endocr. (1988) 116, 273–277
Opioid peptides do not modulate atrial natriuretic peptide or aldosterone release under basal conditions in man
Authors: Borges F. , Anderson J. V. , Volta C. , Perry L. , Drury P. L. , Bloom S. R. , Besser G. M. , Grossman A.
Published: December 2008

The effect of two analogues of [Met]-enkephalin, [d-Ala2,N-Phe4,Met(0)-ol5]-enkephalin and its guanyl derivative, on plasma concentrations of atrial natriuretic peptide (ANP) and serum aldosterone in six normal subjects was investigated. All subjects were given a 1 litre water load to inhibit vasopressin release. Both analogues, when injected i.v. at a dose of 100 μg, stimulated release of prolactin and GH and inhibited serum cortisol; there was no significant change in blood pressure, pulse rate or urine output. Neither plasma concentrations of ANP nor serum aldosterone levels changed significantly after injection of either analogue at a low or high dose. Naloxone, given i.v. as an 8 mg bolus, also failed to alter concentrations of either ANP or aldosterone, while it significantly stimulated the release of serum LH and cortisol. It was concluded that under basal conditions opiate receptors are unable to modulate plasma ANP or serum aldosterone concentrations.

J. Endocr. (1988) 116, 313–317
Receptors for glucagon-like peptide-1(7–36) amide on rat insulinoma-derived cells
Authors: Göke R. , Conlon J. M.
Published: December 2008

Specific binding of 125I-labelled glucagon-like peptide-1(7–36)amide (GLP-1(7–36)amide) to rat insulinoma-derived RINm5F cells was dependent upon time and temperature and was proportional to cell concentration. Binding of radioactivity was inhibited in a concentration-dependent manner by GLP-1(7–36) amide consistent with the presence of a single class of binding site with a dissociation constant (Kd) of 204± 8 pmol/l (mean ± s.e.m.). Binding of the peptide resulted in a dose-dependent increase in cyclic AMP concentrations (half maximal response at 250 ± 20 pmol/l). GLP-1(1–36)amide was approximately 200 times less potent than GLP-1(7–36)amide in inhibiting the binding of 125I-labelled GLP-1(7–36)amide to the cells (Kd of 45±6 nmol/l). Binding sites for GLP-1 (7–36)amide were not present on dispersed enterocytes from porcine small intestine.

J. Endocr. (1988) 116, 357–362
Evidence that angiotensin II is a paracrine agent mediating gonadotrophin-releasing hormone-stimulated inositol phosphate production and prolactin secretion in the rat
Authors: Jones T. H. , Brown B. L. , Dobson P. R. M.
Published: December 2008

Gonadotrophin-releasing hormone (GnRH) stimulated the accumulation of inositol phosphates and prolactin secretion in anterior pituitary cells from young male rats. Saralasin ([Sar1,Ala8]-angiotensin II; a competitive antagonist of angiotensin II) inhibited the increase in both inositol phosphates and prolactin in a dose-dependent manner. Since angiotensin II has been shown to be a potent stimulus for inositol phosphate accumulation and prolactin secretion in the lactotroph, these findings suggest that angiotensin II acts as a paracrine agent, being released from the gonadotroph in response to GnRH and causing the lactotroph to release prolactin through an effect on phosphoinositide metabolism. The ability of GnRH to promote prolactin release was lost in pituitaries from older rats, and the increase in total inositol phosphate accumulation was less. These findings provide evidence of a physiological role for the presence of the renin–angiotensin system within the pituitary gland.

J. Endocr. (1988) 116, 367–371
Modification by pertussis toxin of the responses of bovine anterior pituitary cells to acetylcholine and dopamine: effects on hormone secretion and 86Rb efflux
Authors: Schofield J. G. , Khan A. I. , Wood A.
Published: December 2008

Acetylcholine is known to stimulate the secretion of growth hormone and prolactin and the efflux of 86Rb from bovine anterior pituitary cells: dopamine prevents the stimulation of 86Rb efflux and of prolactin but not growth hormone secretion. The sensitivity of these responses to pertussis toxin has been determined.

Treatment of bovine anterior pituitary cells in primary culture with pertussis toxin (18 h, 100 ng/ml) did not modify the stimulation of prolactin secretion by acetylcholine, but prevented its inhibition by dopamine. In lactotrophs, dopamine but not acetylcholine receptors are therefore coupled to secretion through a pertussis toxin substrate. The stimulation of 86Rb efflux by acetylcholine was also unaffected by pertussis toxin and, again, its inhibition by dopamine was prevented.

Treatment of the cells with pertussis toxin enhanced the secretion of growth hormone in response to acetylcholine. Nitrendepine (1 μmol/l) prevented the cholinergic stimulation of growth hormone but not prolactin secretion from these cells. Acetylcholine increased the cytoplasmic calcium concentration and this rise was enhanced by treatment of the cells with pertussis toxin. Nitrendepine partially inhibited the rise in calcium caused by acetylcholine, and prevented the enhancement of the rise following pertussis toxin treatment.

Cholinergic stimulation of growth hormone therefore depends on calcium entry through nitrendepine-sensitive channels, whereas stimulation of prolactin secretion does not, and in somatotrophs a pertussis toxin substrate may limit calcium entry through these channels. These different sensitivities of somatotrophs and lactotrophs to pertussis toxin and nitrendepine may reflect differences in the properties of the predominant calcium currents in the two cell types.

J. Endocr. (1988) 116, 393–401
Effects of physical endurance training on the plasma renin-angiotensin-aldosterone system in normal man
Authors: Hespel P. , Lijnen P. , Van Hoof R. , Fagard R. , Goossens W. , Lissens W. , Moerman E. , Amery A.
Published: December 2008

The effect of physical endurance training on the plasma renin-angiotensin-aldosterone system was studied in 27 normal sedentary volunteers aged between 20 and 55 years, using a randomized two-period cross-over study design. After 4 months of training (2·5 h/week), peak oxygen uptake and physical working capacity at a heart rate of 130 beats/min were increased by 16% (P<0·01) and 29% (P<0·001) respectively, whereas resting heart rate was decreased by 15% (P<0·001). The plasma noradrenaline concentration and haematocrit were both decreased (P<0·01) after training. For the total group of subjects, the small decreases in plasma renin activity (PRA) and in the plasma concentrations of angiotensin-I, angiotensin-II and aldosterone were not statistically significant. However, the change in PRA during the training period was negatively correlated with the increase in physical working capacity (r=−0·49, P<0·01), suggesting that PRA decreased only in those subjects with the greatest increase in exercise capacity. Also, the change in plasma aldosterone during training was negatively related to the rise in physical working capacity (r=− 0·57, P<0·01). Furthermore, the changes in plasma angiotensin-I (r=0·75), angiotensin-II (r=0·49) and aldosterone (r=0·43) during the training period correlated positively with the change in PRA.

It is concluded that physical endurance training, leading to a substantial gain of physical working capacity, suppresses the plasma renin-angiotensin-aldosterone system in normal man.

J. Endocr. (1988) 116, 443–449
GROWTH HORMONE IS MITOGENIC FOR FETAL MOUSE OSTEOBLASTS BUT NOT FOR UNDIFFERENTIATED BONE CELLS
Authors: Slootweg M.C. , van Buul-Offers S.C. , Herrmann-Erlee M.P.M. , van der Meer J.M. , Duursma S.A.
Published: December 2008

More evidence has recently been obtained indicating that growth hormone (GH) has a direct effect on bone. However, it is not clear which cell type reacts to the hormone. The present study used osteoblast-like cells derived from sequentially digested fetal mouse calvaria. Separately cultured tractions resulted in populations enriched in cells with a more or a less differentiated phenotype. The results showed that GH acts on the cells released last, i.e. those with more characteristics of the osteoblast. In these cells, GH induced strong mitogenic activity. Prolactin was not active.
Re-evaluation of the intratesticular level of testosterone required for quantitative maintenance of spermatogenesis in the rat
Authors: Sharpe R. M. , Donachie K. , Cooper I.
Published: December 2008

The amount of testosterone required for quantitative maintenance of spermatogenesis has been re-evaluated using techniques aimed at minimizing the synthesis of testosterone after removal of the testis. Adult male rats were treated with ethane dimethane-sulphonate (EDS) to destroy the Leydig cells, and were supplemented with 25, 5 or 1 mg testosterone esters by injection every 3 days for 21 days. Serum hormone levels, testicular morphology and spermatogenesis were assessed and the intratesticular levels of testosterone compared in testes either removed under ether anaesthesia and placed in liquid nitrogen (right testis) or removed after collection of blood and placed in ice (left testis). Data for testosterone-supplemented rats were compared with those for control rats and rats treated with EDS alone.

All doses of testosterone suppressed LH and FSH levels in serum to within the hypophysectomized range, and Leydig cell regeneration in EDS-treated rats was prevented completely. Treatment of EDS-injected rats with 25 or 5 mg testosterone maintained testicular weight, the number of germ cells and the diameter of seminiferous tubules at stage VII within or above the control range, although there was a significant increase in the number of degenerating pachytene spermatocytes at stage VII with 5 but not 25 mg testosterone; none of these parameters was maintained at control levels by a dose of 1 mg testosterone.

Levels of testosterone in testosterone-supplemented rats differed little between testes collected in ice and liquid nitrogen, but in controls and rats treated with EDS alone, testosterone levels were overestimated by 75 and 27% respectively when comparing testes collected in ice with those collected in liquid nitrogen. This suggests that synthesis of testosterone does occur after removal and cooling of the testes. Using the data for testes collected in liquid nitrogen, the present results suggest that intratesticular levels of testosterone need to be maintained at 24–46% of control values (i.e. higher than previously shown) for quantitative maintenance of spermatogenesis, although it is argued that even these values probably still represent underestimates.

J. Endocr. (1988) 117, 19–26
Characterization of a plasminogen activator inhibitor induced by glucocorticoids in immature bovine Sertoli cell-enriched cultures
Authors: Coombs R. J. , Jenkins N.
Published: December 2008

Plasminogen activation has been shown to be inhibited by the cell-specific production of a number of protease inhibitors belonging to the serine protease inhibitor family. In the bovine testis this inhibitor production is induced by glucocorticoids. Monospecific antibodies raised against the three known classes of plasminogen activator inhibitor were used to identify which type of inhibitor was secreted by bovine Sertoli cell-enriched cultures. Immunoblot analysis and [35S]methionine labelling of newly synthesized proteins revealed that a novel protein with an apparent molecular weight of 49 kDa, which shares antigenic determinants with placental and macrophage PAI and fibroblast protease nexin, is secreted in response to dexamethasone stimulation. This protein was shown by immuno-adsorption to be a functionally active inhibitor of both tissue-type and urokinase-type plasminogen activators.

J. Endocr. (1988) 117, 69–74
Purification, partial sequences and properties of chicken insulin-like growth factors
Authors: Dawe S. R. , Francis G. L. , McNamara P. J. , Wallace J. C. , Ballard F. J.
Published: December 2008

Insulin-like growth factor-I (IGF-I) and IGF-II have been purified to homogeneity from chicken serum as a step towards the characterization of the roles for these peptides in the growth process. Chicken IGF-I had about half the efficacy of bovine/human IGF-I in a bioassay and in radioimmunoassays with bovine IGF-I as radioligand. Chicken IGF-II competed for the binding of bovine IGF-II to cell receptors while chicken IGF-I reacted minimally in this IGF-II radioreceptor assay. Further evidence of homology was obtained by N-terminal sequence analysis of the first 31 and 35 amino acids of chicken IGF-I and IGF-II respectively. Chicken IGF-I had the same N-terminal as human IGF-I, with the exception of the substitution of serine for asparagine at residue 26. Chicken IGF-II had a unique N-terminal tetrapeptide Tyr-Gly-Thr-Ala, but from residues 5–30 the sequence was identical to that reported for residues 6–31 of human IGF-II. Substitutions also occurred corresponding to residues 32, 33, 35 and 36 of human IGF-II. A variant form of chicken IGF-II that had the same N-terminal pentapeptide as human IGF-II was also detected.

J. Endocr. (1988) 117,173–181
Plasma half-lives of native and modified insulin-like growth factor-I in lambs
Authors: Francis G. L. , McNamara P. J. , Filsell O. H. , Ballard F. J.
Published: December 2008

The clearance of labelled insulin-like growth factor-I (IGF-I) has been measured in lambs following acid gel-permeation chromatography and immunoprecipitation of plasma samples. The half-lives obtained in three experiments were between 5 and 7 h. Chromatography at neutral pH on a Fractogel HW55(S) column demonstrated that all the radioactivity associated with undegraded peptide in plasma was bound to a carrier protein. Similar studies with IGF-I that had been reduced by prior dithiothreitol treatment showed that two-thirds of the initial radioactivity in plasma decayed with a much shorter half-life and represented material that did not bind to carrier proteins in plasma. The remaining radioactivity was both associated with a binding protein and exhibited the characteristically long half-life of the native growth factor. Analysis of plasma samples using reversed-phase chromatography demonstrated that the radioactive component with a long half-life was IGF-I while that with a short half-life had been reoxidized to an incorrect form of the growth factor. When reoxidation of reduced IGF-I was blocked by S-carboxymethylation before injection of the radioactive peptide into lambs, it remained unbound in plasma and had a 0·8–0·9 h half-life. We suggest that reduced IGF-I only associates with the binding protein upon oxidation and correct folding and that this association is necessary in order for IGF-I to have a relatively long half-life.

J. Endocr. (1988) 117, 183–189
Aldosterone secretion and adrenal angiotensin II receptors in the Brattleboro rat
Authors: Laulin J. P. , Simonnet G. , Brudieux R. , Carayon A. , Vincent J. D.
Published: December 2008

The basal secretion of aldosterone, measured in adrenal venous blood, was three- to fourfold lower in Brattleboro than in Long–Evans rats used as controls. Infusion of a low dose of angiotensin II (1 ng/min per 100 g body/wt) to Long–Evans rats caused a fourfold increase in aldosterone release but neither the low dose nor a tenfold higher dose changed the rate of release in Brattleboro rats. Only a very high dose (300 ng/min per 100 g body wt) succeeded in increasing the secretion of aldosterone in Brattleboro rats but throughout the time-course of the infusion, secretion remained about fivefold lower than in Long-Evans rats and the incremental response was reduced by 74·9%. Adrenal zona glomerulosa angiotensin II receptor sites had similar affinity and maximum binding capacity in the two groups of rats. It is suggested that the reduced corticosteroidogenic capacity of the adrenal cortex of Brattleboro rats results from an impairment of the post-receptor mechanisms involved in the biosynthesis of aldosterone.

J. Endocr. (1988) 117, 215–221
Withdrawal of endogenous somatostatin induces secretion of growth hormone-releasing factor in rats
Authors: Miki N. , Ono M. , Shizumen K.
Published: December 2008

Secretion of GH occurs in episodic bursts under the dual control of two hypothalamic peptides, GH-releasing factor (GRF) and GH-inhibiting factor (somatostatin, SRIF). Recent studies in rats suggest that episodic GH secretion is generated by the periodic release of GRF, which is associated with the simultaneous withdrawal of SRIF secretion. To test the possibility that GRF discharge is functionally coupled with the withdrawal of SRIF, we investigated whether acute withdrawal of SRIF can induce GRF release by the rat hypothalamus using highly specific antisera against SRIF and rat GRF. In conscious unrestrained rats, i.v. administration of SRIF antiserum at the period of the GH trough induced a rapid onset of the GH secretory surge with a peak value of 309 ± 67 μg/l (mean ± s.e.m.) 30 min after injection. Pretreatment with antiserum to rat GRF resulted in a ∼83% suppression of the GH surge induced by SRIF antiserum without affecting the trough GH values. GRF antiserum also significantly inhibited the spontaneous GH surge. In urethane-anaesthetized rats, as in conscious rats, an acute phasic GH release was caused by SRIF antiserum despite the interference of anaesthesia with spontaneous GH secretion. A further surge-like GH secretion was not restored during the next several hours, however, with the GH secretory profile being characterized by a tonic increase in the baseline levels of GH. In the anaesthetized rat antiserum to rat GRF, having no effect on basal GH levels, similarly inhibited by ∼66% the acute GH surge induced by SRIF antiserum and decreased by about 30% the later sustained rise in GH.

These results indicate that an acute rather than a chronic withdrawal of SRIF can trigger the phasic discharge of GRF by the hypothalamus, and raise the possibility that SRIF, originally isolated as a hypothalamic hypophysiotrophic GH-inhibiting factor, also acts as a GRF-inhibiting factor within the hypothalamus. We suggest that the episodic GH secretion may be initiated by an acute disinhibition of GRF secretion caused by the sudden withdrawal of SRIF.

J. Endocr. (1988) 117, 245–252
Inhibin secretion by the sheep ovary during the luteal and follicular phases of the oestrous cycle and following stimulation with FSH
Authors: Tsonis C. G. , McNeilly A. S. , Baird D. T.
Published: December 2008

The secretion of oestradiol and inhibin were measured during the follicular and luteal phase of the cycle by a sensitive bioassay using sheep pituitary cells in culture in four ewes in which the left ovary had been autotransplanted to the neck. On day 12 of the cycle, premature luteal regression was induced with an injection of 100 μg cloprostenol (prostaglandin F2α analogue; PG) and ovarian venous blood was collected every 4 h for 72 h. These same four ewes were infused in the ensuing cycle with NIH-oFSH-S14 at 10 μg/h for 48 h immediately after an injection of PG and sampled as above.

During the luteal phase ( − 2 h before PG) both in the control and FSH-infused cycles the inhibin secretion rate (SR) was 27–45 units/min. After PG injection, the inhibin SR declined with time to reach 3·6–5 units/min at the onset of the LH surge (60 h after PG) in the control cycle. In contrast, in the following cycle infusion of FSH after PG injection caused a slight increase in the inhibin SR which then remained raised at 42–50 units/min for up to 60 h after PG. In the late follicular phase the oestradiol SR was greater in the FSH-infused than in the control cycles, indicating multiple follicular development. In the FSH-infused cycle the preovulatory surges of LH and FSH were markedly attenuated.

These data demonstrate that (1) inhibin SR is high during the luteal phase suggesting that the sheep corpus luteum secretes inhibin, (2) in the control cycle inhibin SR declines during follicular maturation at a time when oestradiol SR is increasing but FSH levels are decreasing, and (3) exogenously administered FSH stimulates the secretion of inhibin from the ovary during the follicular phase.

J. Endocr. (1988) 117, 283–291