bluuebunny/crossref_metadata_2025 huggingface dataset:
Increase in milk secretion and mammary blood flow by intra-arterial infusion of insulin-like growth factor-I into the mammary gland of the goat
Authors: Prosser C. G. , Fleet I. R. , Corps A. N. , Froesch E. R. , Heap R. B.
Published: December 2008

The close-arterial infusion of free insulin-like growth factor-I (IGF-I; 1·1 nmol/min) for 6 h into the pudic artery supplying one mammary gland of lactating goats caused a 25±6% (mean ± s.e.m., n = 6) increase in the rate of milk secretion of that gland. The increase in the rate of milk secretion in the adjacent non-infused gland (14±4%) was not significantly different from that observed during saline infusion (4±5%). Blood flow to the infused gland was increased from 378±26 ml/min 1 h before to 487±56 ml/min approximately 5 h after the start of the infusion of IGF-I, declining to 420±44 ml/min approximately 2 h after the end of the infusion. The total concentration of IGF-I (free and bound) in milk of the infused gland was significantly higher than that of the non-infused gland. The concentrations of IGF-I in carotid arterial plasma samples increased during IGF-I infusion from a mean value of 32±2 nmol/l before to a maximum of 49±3 nmol/l 5 h after the infusion commenced. Circulating concentrations of total IGF-I declined slowly after the infusion with an estimated half-life of 5 h. Infusion of saline alone did not alter mammary blood flow or the concentration of total IGF-I in milk or plasma. The results indicate that the infusion of free IGF-I into the mammary arterial supply enhances milk secretion and mammary blood flow in intact, conscious goats. The more pronounced effect in the infused compared with the non-infused gland suggests that free IGF-I acts directly on the mammary gland. The response in the non-infused gland was attenuated presumably due to association of IGF-I with plasma binding proteins during recirculation.

Journal of Endocrinology (1990) 126, 437–443
Dexamethasone pretreatment of rat insulinoma cells decreases binding of glucagon-like peptide-1(7–36)amide
Authors: Richter G. , Göke R. , Göke B. , Arnold R.
Published: December 2008

The effect of dexamethasone on binding of glucagonlike peptide-1(7–36)amide (GLP-1(7–36)amide) to rat insulinoma-derived cells (RINm5F) was investigated. Preincubation of RINm5F cells with dexamethasone (100 nmol/l) for 24 h resulted in a decrease of GLP1(7-36)amide binding to 55·0±8·16% (mean ± s.e.m.), incubation for 48 h to 39·1±1·76%, and for 72 h to 15·5±4·35% of maximal binding. The GLP-1(7–36)amide-induced stimulation of cyclic AMP (cAMP) production was significantly decreased to 61·03±7·4% of maximum production in cells pretreated with dexamethasone (100 nmol/l) for 48 h. The decreased binding was due to a reduction of the receptor number while the receptor affinity remained unchanged. These inhibitory effects on binding and cAMP formation induced by dexamethasone were completely abolished when the antiglucocorticoid RU 38486 (100 nmol/l) was added during preincubation with dexamethasone. RU 38486 alone had no effects. Our data suggest that the biological action of GLP-1(7–36) amide at the B-cell may be modified by glucocorticoids.

Journal of Endocrinology (1990) 126, 445–450
Insulin-like effect of vanadyl ion on streptozotocin-induced diabetic rats
Authors: Sakurai H. , Tsuchiya K. , Nukatsuka M. , Sofue M. , Kawada J.
Published: December 2008

Recent studies have indicated that the blood glucose level of rats with streptozotocin (STZ)-induced diabetes (type 1) is normalized without an increase in the plasma insulin level by administration of sodium orthovanadate in the drinking water. The mechanism of this insulin-like effect of vanadate is unknown.

In this study, we investigated whether vanadyl ion, which is less toxic than vanadate to rats, also has an insulin-like effect in rats with STZ-induced diabetes. When rats with STZ-induced diabetes were given a daily i.p. injection of vanadyl sulphate (9·3 and 4·6 mg vanadium/kg body weight), their blood glucose level decreased from about 22·2 to about 7·2 mmol glucose/l within 2 days and remained low for at least 12 weeks. This treatment did not affect their low plasma insulin level. Quantitative electron spin resonance (ESR) spectrometry showed that most of the vanadium (about 90%) in their tissues was present as a vanadyl form (VO2+). ESR analysis also showed that the vanadyl ion in tissues was bound endogenously with four oxygen ligands from either water or oxyamino acid residues in proteins. Vanadyl sulphate accelerated glucose incorporation into adipocytes of rats, suggesting that the action of vanadyl ion is peripheral. Interestingly, vanadyl sulphate at a high concentration (about 10 mmol/l) was more effective than insulin in enhancing glucose uptake.

This study demonstrated that: (1) vanadyl sulphate (+ 4 oxidation state), like vanadate ion, normalizes the blood glucose levels of rats with STZ-induced diabetes; (2) the action of vanadyl ion is peripheral; and (3) the active form of vanadium for an insulin-like effect may be a vanadyl form, not vanadate.

Journal of Endocrinology (1990) 126, 451–459
Effects of trenbolone acetate and testosterone on growth and on plasma concentrations of corticosterone and ACTH in rats
Authors: Sillence M. N. , Rodway R. G.
Published: December 2008

The effects of trenbolone acetate (TBA) on growth and on plasma concentrations of corticosterone were examined in male and female rats. At 5 weeks of age, rats were injected with TBA (0·8 mg/kg) dissolved in peanut oil, or with oil alone, daily for 10 days. In female rats, TBA caused an increase in weight gain (20–38%), a reduction in adrenal weight (19%) and a reduction in plasma concentrations of corticosterone (55%). In contrast, TBA-treated male rats showed no significant increase in weight gain, no significant change in adrenal weight and no reduction in plasma concentrations of corticosterone.

The mechanism by which adrenal activity was suppressed in TBA-treated female rats was examined and the response compared with that to testosterone. Female rats (8 weeks old) were injected daily either with oil vehicle, TBA (0·8 mg/kg) or testosterone propionate (0·8 mg/kg). Testosterone increased weight gain (24%), but the growth response to TBA treatment was significantly greater (97%). A reduction in plasma concentrations of corticosterone (45%) was again observed in response to TBA. However, testosterone increased plasma concentrations of corticosterone (52%) above those of control values. Neither androgen affected plasma concentrations of ACTH.

Finally, the effects of TBA were examined in 6-week-old female rats, to characterize further the apparent age-related increase in responsiveness. The growth response of 6-week-old rats (60–74%) was intermediate between that seen in 5- and 8-week-old animals.

It is concluded that part of the anabolic activity of TBA may be related to a reduction in circulating concentrations of corticosterone. The effect of TBA on corticosterone concentrations differs from that of the natural androgen, testosterone, and does not appear to be mediated by a reduction in plasma concentrations of ACTH.

Journal of Endocrinology (1990) 126, 461–466
Inhibin secretion during the ovulatory cycle and pregnancy in the common marmoset monkey
Authors: Smith K. B. , Lunn S. F. , Fraser H. M.
Published: December 2008

Changes in plasma concentrations of immunoreactive inhibin in the reproductively cyclic, pregnant and ovariectomized female marmoset monkey (Callithrix jacchus) were measured with a heterologous radioimmunoassay. The pattern of inhibin secretion in five marmosets studied individually during four consecutive cycles was shown to resemble that of progesterone. In these animals, data were pooled according to stage of cycle on the basis of plasma progesterone concentrations. Mean values for inhibin were 5465 and 4972 U/l during the early and late follicular phase. Concentrations rose during the luteal phase to 8431, 12 246 and 12 557 U/l for the early, mid- and late luteal phase respectively. The hormonal profile of inhibin during the normal cycle is similar in both marmoset and stumptailed macaque; however, the marmoset has a 28-fold greater level of inhibin during the luteal phase.

In six marmosets in which pregnancy occurred, inhibin concentrations showed no decline at the end of the conceptual cycle and remained increased with respect to the follicular phase throughout the subsequent gestation. Inhibin levels were non-detectable (< 1000 U/l) in ovariectomized and acyclic marmosets.

These results suggest that the corpus luteum is the major source of inhibin in this New World monkey, in common with man and the Old World primates.

Journal of Endocrinology (1990) 126, 489–495
An insulin-like growth factor-binding protein purified from medium conditioned by a human lung fibroblast cell line (He[39]L) has a novel N-terminal sequence
Authors: Forbes B. , Ballard F. J. , Wallace J. C.
Published: December 2008

We have identified a novel insulin-like growth factor (IGF)-binding protein secreted into the culture medium of a human lung fibroblast cell line (He[39]L). This binding protein was purified by S-Sepharose cation exchange chromatography, IGF affinity chromatography and reverse-phase high-performance liquid chromatography. Analysis of the He[39]L-binding protein on silver-stained polyacrylamide gels and by ligand blotting showed that it had a molecular weight of 32 kDa under non-reducing conditions. In charcoal competition binding assays, IGF-II competed at lower concentrations than IGF-I for binding to the He[39]L-binding protein and the more potent form of IGF-I (des-(1–3)-IGF-I) was not bound. This is a similar IGF binding pattern to that of the bovine IGF-binding protein-2 (bIGFBP-2). However, immunoblotting with an antibody to bIGFBP-2 demonstrated that the He[39]L-binding protein is not immunochemically related to bIGFBP-2. It is a glycosylated protein, having N-acetyl-glucosaminyl sugars detected by wheatgerm agglutinin affinity chromatography. Of the first 15 N-terminal amino acids of the He[39]L-binding protein, 13 are identical to the 15 amino acid sequence of a recently sequenced cerebrospinal fluid-binding protein. However, the total He[39]L-binding protein sequence (25 amino acids) showed no homology to other previously sequenced binding proteins (IGFBP-1, IGFBP-2 and IGFBP-3). We conclude that the He[39]L-binding protein is a novel binding protein.

Journal of Endocrinology (1990) 126, 497–506
Basic fibroblast growth factor affects DNA synthesis and cell function and activates multiple signalling pathways in rat thyroid FRTL-5 and pituitary GH3 cells
Authors: Black E. G. , Logan A. , Davis J. R. E. , Sheppard M. C.
Published: December 2008

We have used a recombinant human basic fibroblast growth factor (basic FGF) to study its effects on cell proliferation, gene expression and accumulation of cyclic AMP (cAMP) and inositol phosphates in two well-characterized endocrine cell lines, FRTL-5 rat thyroid and GH3 rat pituitary cells. Basic FGF induced a dose-dependent increase in mitogenesis (assessed by measuring incorporation of [3H]thymidine) in FRTL-5 cells (40 ng basic FGF/ml increased mitogenesis above the control value by 2148±108% (mean ± s.e.m.), but inhibited mitogenesis in GH3 cells at all doses (85±4% of control with 40 ng basic FGF/ml)). Thyroglobulin mRNA concentration was increased in FRTL-5 cells (126±6% of control with 40 ng basic FGF/ml) as was prolactin mRNA in GH3 cells (246±11% of control with 40 ng basic FGF/ml), but GH mRNA in GH3 cells was not significantly affected by any dose of basic FGF. Intracellular cAMP was reduced by basic FGF in both FRTL-5 and GH3 cells (40 ng bFGF/ml giving 80±5% of the control value in FRTL-5, and 67±15% of the control value in GH3 cells) despite increased levels when FRTL-5 cells were stimulated with 150 μU TSH/ml (5645±484% of control) or GH3 cells were stimulated by 10 μmol forskolin/1 (3347±396% of control). In both FRTL-5 and GH3 cells, accumulation of [3H]inositol phosphates was increased by 40 ng basic FGF/ml (201±6 and 330±51% of control values respectively).

We have shown that basic FGF has different effects on mitogenesis in the two cell lines; gene expression and accumulation of inositol phosphates were increased in both, whereas the intracellular concentration of cAMP was decreased. The actions of basic FGF may be mediated through both inhibition of adenylate cyclase and hydrolysis of phosphatidyl inositol bisphosphate as has been proposed for 3T3 fibroblasts. Our data suggest that there may be a physiological role for basic FGF in both thyroid and pituitary tissue.

Journal of Endocrinology (1990) 127, 39–46
Possible oncostatic action of cysteamine on the pituitary glands of oestrogen-primed hyperprolactinaemic rats
Authors: Jeitner T. M. , Oliver J. R.
Published: December 2008

Cysteamine was investigated for its potential to reduce the size and secretion of oestrogen-primed hyperprolactinaemic rat pituitary glands. Subcutaneous administration of 80 and 120 mg cysteamine/kg significantly reduced plasma prolactin concentrations by 58 and 91% respectively, after 4 h. Administration of cysteamine (60 mg s.c./kg body weight per day) for 10 days, to rats which had received an injection of 2 mg oestradiol benzoate on day 1, resulted in a significant reduction in pituitary mass (19%) and GH concentration (21%).

Oral administration of 60 mg cysteamine/kg body weight to hyperprolactinaemic rats also produced a significant reduction in plasma prolactin of 94% after 2 h. Oral administration of 60 mg cysteamine/kg body weight per day to rats for a 20-day period, during which they had received two injections of 2 mg oestradiol benzoate on day 1 and day 14 of treatment, resulted in a significant reduction in pituitary mass (29%) and the concentration of trunk blood prolactin concentration (35%). However, when oral cysteamine (60 mg cysteamine/kg body weight per day) was given for 20 days to rats which had been treated with 2 mg oestradiol benzoate once every 14 days over a 90-day period, it caused no change in pituitary weight, prolactin or GH concentration, or the concentration of prolactin in trunk blood. Encapsulating cysteamine in liposomes and subsequent oral administration at 60 mg/kg body weight per day for 10 days to rats which had received five injections of 2 mg oestradiol benzoate once every 14 days over a 80-day period, caused a significant reduction in pituitary weight (36%) and prolactin concentration (28%) as well as prolactin concentration in trunk blood (22%). Liposome-entrapped cysteamine was also able to reduce plasma prolactin concentrations in a time- and dose-dependent manner in hyperprolactinaemic rats. The profile of plasma prolactin depletion produced by liposome-encapsulated cysteamine was different from that of free cysteamine and may account for its ability to reduce the size and secretion of pituitaries from chronically hyperprolactinaemic rats.

Journal of Endocrinology (1990) 127, 119–127
Galactopoietic and mammogenic effects of long-term treatment with bovine growth hormone and thrice daily milking in goats
Authors: Knight C. H. , Fowler P. A. , Wilde C. J.
Published: December 2008

Starting in mid-lactation, goats were treated daily for 22 weeks with 0·15 mg recombinant bovine GH (bGH)/kg, or an equivalent volume of vehicle. One gland of each goat was milked thrice daily throughout treatment, the other twice daily. Mammary differentiation was studied in biopsy samples obtained before treatment and after 3 and 22 weeks of treatment, by determination of in-vitro synthesis rates of milk constituents and measurement of enzyme activities. Mammary growth was measured using a whole-body imaging technique (magnetic resonance imaging; MRI).

bGH caused an immediate and sustained increase in milk yield of approximately 23% overall, whilst the glands milked thrice daily produced approximately 14% more than the control glands milked twice daily. The effects of the combined treatment were additive, but not synergistic. A synergistic effect of the combined treatment resulted in a significant improvement in lactation persistency.

A stimulatory effect of milking frequency on mammary enzyme activities was evident only in bGH-treated goats at 3 weeks, but in both groups at 22 weeks. Synthesis rates of casein and lactose were increased at 3 weeks only by the combined treatment. Thus bGH accelerated or augmented the differentiative response to thrice daily milking. Mammary parenchyma volume, estimated by MRI, increased significantly during the first 12 weeks of bGH treatment and remained higher throughout the rest of the treatment period. Cell number was estimated from parenchyma volume and DNA concentration; this decreased significantly in the controls between weeks 1 and 22, but remained constant in the bGH group. In nine of the ten goats, parenchyma volume and cell number increased in the gland milked thrice daily relative to the control gland milked twice daily during the course of the experiment. Thus bGH stimulated growth of the mammary gland over and above that induced by the frequent milking. The absence of any detectable increase in thymidine incorporation suggests that this growth consisted of cellular hypertrophy rather than hyperplasia.

Journal of Endocrinology (1990) 127, 129–138
Comparisons of various acidic treatments of bovine serum on insulin-like growth factor-I immunoreactivity and binding activity
Authors: Lee C. Y. , Henricks D. M.
Published: December 2008

Untreated serum exhibited two forms of insulin-like growth factor-I (IGF-I)-binding protein complexes during gel chromatography: one of Mr 150 000 and the other of Mr 40 000–45 000. The majority of the immunoreactive IGF-I was associated with the Mr 150 000 complex. Following acid-ethanol extraction of serum, the binding activity at Mr 150 000 disappeared and a reduced binding activity appeared in the albumin size range. Acid incubation of serum was slightly less effective than acid-ethanol extraction in reducing the binding activity. Acid-ethanol-extracted or acid-incubated serum were parallel to IGF-I standard in the dose–response displacement of iodinated IGF-I. Gel filtration of serum with 1 mol acetic acid/l almost completely separated IGF-I and the binding proteins. Binding-protein fractions from gel filtration interfered with the immunoreactivity of IGF-I with its antibodies, causing a non-parallel displacement curve in the radioimmunoassay (RIA). Serum IGF-I could be isolated as a single peak by high performance C18 reverse-phase liquid chromatography (HPLC). The concentrations of IGF-I measured in bovine sera by RIA were similar between acid gel filtration and HPLC; the concentrations by acid-ethanol extraction and acid incubation being about 30% smaller than those measured with former methods. The lower concentration of IGF-I measured in bovine serum with acid-ethanol extraction or acid incubation appears to be due to interference of IGF-binding proteins not removed by either treatment.

Journal of Endocrinology (1990) 127, 139–148
Substrate interactions in the development of insulin resistance in type II diabetes and obesity
Authors: Sugden M. C. , Holness M. J.
Published: December 2008

Introduction

Theories for the mechanisms underlying the development of insulin resistance have included defects in insulin binding, inhibition of insulin receptor tyrosine kinase, and impaired translocation of glucose across the plasma membrane. However, little attention has been paid to the possibility that altered reciprocal regulatory interactions between lipid and carbohydrate fuels may underly the development of insulin resistance. We would like to review recent developments in metabolic regulation which indicate that this neglected aspect of intermediary metabolism may have more widespread physiological significance than hitherto suspected.

The major pathways of glucose utilization are storage (glycogen), non-oxidative degradation (glycolysis) and oxidative degradation. It has been demonstrated in post-absorptive man by indirect calorimetry that the ability of insulin to stimulate non-oxidative disposal of glucose is decreased by the prior oxidation of lipid (Thiebaud, DeFronzo, Jacot et al. 1982). In these studies, a neutral lipid emulsion was infused before insulin concentrations were raised by
Effects of modifying gonadotrophin-releasing hormone input before and after the oestrogen-induced LH surge in ovariectomized ewes with hypothalamo-pituitary disconnection
Authors: Phillips D. J. , Cummins J. T. , Clarke I. J.
Published: December 2008

The patterns of gonadotrophin-releasing hormone (GnRH) input to the pituitary gland that affect the expression of a positive-feedback event by oestrogen on LH secretion were investigated in ovariectomized ewes with hypothalamo-pituitary disconnection (HPD). In experiment 1, ovariectomized HPD ewes were given hourly i.v. pulses of 250 ng GnRH and an i.m. injection of 50 μg oestradiol benzoate (OB). The ewes were given a bolus pulse of 2·25 μg GnRH 16 h after injection of OB, followed by half-hourly pulses of 250 ng GnRH for 14 h (treatment A). The LH surge response was significantly (P <0·05) greater in these ewes compared with that in ewes given a continuous infusion of GnRH (250 ng/h) after the OB injection, followed by a continuous infusion of 500 ng GnRH/h after the bolus pulse of GnRH (treatment B). When no GnRH was administered after the OB injection, except for the bolus pulse of GnRH (treatment C), the surge response was significantly (P <0·05) reduced compared with that in treatment A, and was reduced compared with treatment B. These data suggest that GnRH pulses are important in the generation of the OB-induced LH surge, but that a baseline secretory component can prime the pituitary to some extent. experiment 2, a doubling of the continuous infusion dose of GnRH used in treatment B to 500 ng/h before the bolus pulse of GnRH and to 1 μg/h afterwards (treatment D) gave a similar response compared with treatment A, suggesting that if the baseline input of GnRH is of sufficient magnitude, it can overcome the lack of pulsatile input. In experiment 3, halving the GnRH pulse amplitude used in treatment A from 250 to 125 ng (treatment E) did not reduce the LH surge response, implying that when the GnRH input is in a pulsatile mode, the amplitude of GnRH pulses is less important than the pulsatile nature per se. In experiment 4, removal of GnRH input after the bolus pulse of GnRH (treatment F) significantly (P <0·05) reduced the surge response compared with when pulses were maintained (treatment A), indicating that GnRH input is still required once the LH surge has been initiated. Collectively, these experiments show that several forms of GnRH delivery, both pulsatile and baseline, can result in the full expression of a positive-feedback response in ovariectomized ewes treated with oestrogen.

Journal of Endocrinology (1990) 127, 223–233
Synergism of testosterone propionate with growth hormone in promoting growth of hypophysectomized rats: effect of sexual differentiation
Authors: Klindt J. , Ford J. J. , Macdonald G. J.
Published: December 2008

The effect of testosterone propionate (TP), alone and in combination with porcine GH, on the growth of hypophysectomized rats was investigated. An initial study determined doses of TP and GH which would result in a synergistic response. Hypophysectomized male rats, approximately 40 days of age, received GH at doses of 5, 25 and 62·5 μg/day administered in two injections/day at 08.00 and 16.00 h. At all doses of GH, administration of TP at 100 μg/day significantly enhanced the GH-stimulated rate of growth. This growth enhancement by TP was greatest in combination with GH at 25 μg/day. In a subsequent study, growth responses to 25 μg GH/day and 100 μg TP/day were examined in animals with differing degrees of sexual differentiation. Sex groups were: intact males, males castrated at 11 days of age and females administered 100 μg TP at 3 days of age (masculinized rats), and males castrated at 2 days of age and normal females (non-masculinized rats). In all sex groups, growth of hypophysectomized rats was stimulated by GH. Genetic sex and masculinization did not influence the response to GH. Masculinized hypophysectomized rats exhibited significantly greater rates of growth and final live, empty body, liver and kidney weights than non-masculinized hypophysectomized rats. All sex groups other than normal females responded synergistically to the combination treatment of GH plus TP. Rats that experienced neonatal exposure to testosterone became programmed to respond to testosterone and demonstrated greater rates of growth and body and organ weights when administered the combination of GH plus TP. These data indicate that TP synergizes with GH to promote growth of hypophysectomized rats appropriately programmed to respond. The ability to manifest a synergistic response is a differentiated trait dependent upon exposure to testosterone during the appropriate period of development. The time of differentiation of this ability to respond to testosterone occurs earlier than that for differentiation of body growth.

Journal of Endocrinology (1990) 127, 249–256
The antagonistic effect of exogenous LH pulses on FSH-stimulated preovulatory follicle growth in ewes chronically treated with a gonadotrophin-releasing hormone agonist
Authors: Picton H. M. , Tsonis C. G. , McNeilly A. S.
Published: December 2008

The hypogonadotrophism model induced by the chronic administration of gonadotrophin-releasing hormone (GnRH) agonist was used to investigate the effects of different concentrations of FSH with or without LH pulses on the stimulation of follicular development in the ewe. Continuous administration of an agonist (buserelin) by osmotic minipump to thirty-six Welsh Mountain ewes from the early luteal phase for 5 weeks resulted in a sustained suppression of the plasma concentration of FSH and inhibited the pulsatile release of LH. The inhibition of gonadotrophin secretion was due to the desensitization and/or down-regulation of pituitary gonadotroph function, since the agonist-treated animals showed no response to a challenge of 1 μg GnRH.

During week 6 of agonist treatment, ewes were infused with either 4-hourly pulses of ovine LH (9 μg/pulse), low concentrations of ovine FSH (3 μg/h) or high concentrations of FSH (9 μg/h) alone or with 4-hourly pulses of LH. After 5 days of gonadotrophin infusion, there was no difference between the mean number of follicles per ewe from the animals treated with LH alone, low concentrations of FSH with or without LH pulses or the high concentration of FSH alone compared with the mean number of follicles from control ewes on day 8 of the luteal phase. Infusion of the high concentration of FSH alone stimulated the development of an increased number of large oestrogenic follicles (follicles > 2·5 mm in diameter and secreting > 3·7 nmol oestradiol/h in vitro) compared with control ewes. The addition of high-amplitude LH pulses to the infusion of the high concentration of FSH prevented follicles developing beyond 2·5 mm in diameter, but doubled the number of small follicles (≤2·5 mm) present in the ovaries.

These results show that normal follicular development can be induced by physiological concentrations of FSH alone in the absence of pulsatile LH release. The addition of high-amplitude LH pulses antagonized this stimulatory effect of FSH on follicle growth in the ewe.

Journal of Endocrinology (1990) 127, 273–283
Epidermal growth factor in small antral ovarian follicles of pregnant women
Authors: Westergaard L. G. , Andersen C. Yding , Byskov A. G.
Published: December 2008

Levels of epidermal growth factor (EGF) and steroids were measured by radioimmunoassay in follicular fluid (FF) aspirated from 114 small antral follicles with diameters from 1 to 6 mm and in serum from 19 women undergoing Caesarean section at term. Concentrations of EGF in FF were inversely and significantly correlated to follicular size, being 4·7±0·4 (mean ± s.e.m.) nmol/l in follicles of 1–2 mm in diameter and declining to 2·2±0·2 and 1 ·4±0·2 nmol/l in follicles of 3–4 mm and 5–6 mm in diameter respectively. The mean ± s.e.m. concentration of EGF in serum (0·7±0·03 nmol/l) was significantly lower than that in FF. Levels of EGF, progesterone and oestradiol in FF were not significantly correlated to one another. In contrast to EGF, levels of progesterone and oestradiol in FF did not vary significantly with follicular diameter in these small follicles.

On the basis of these results we suggest that EGF is synthesized in small human antral follicles, and that EGF stimulates granulosa cell proliferation and follicle growth up to 6 mm in diameter. Furthermore, the high intrafollicular levels of EGF may protect the small follicles against untimely effects of high levels of FSH, for instance during the mid-cycle surge of gonadotrophins.

It is concluded that EGF plays an important role as an autocrine and/or paracrine regulator of development of small antral follicles in women.

Journal of Endocrinology (1990) 127, 363–367
Influence of steroid hormone treatments or pregnancy on [3H]prazosin and [3H]rauwolscine binding to myometrial α-adrenoceptors in the ewe
Authors: Vass-Lopez A. , Garcia-Villar R. , Lafontan M. , Toutain P. L.
Published: December 2008

The adrenergic antagonists [3H]prazosin and [3H] rauwolscine were used to identify α1- and α2-adrenoceptors respectively in the ovine myometrium. Ewes were allocated to four groups according to steroid hormone treatments or physiological status, namely ovariectomized ewes either as untreated controls, treated with oestradiol-17β or progestagen plus oestradiol-17β, and pregnant ewes at mid-gestation. Binding of both [3H]prazosin and [3H]rauwolscine to membrane preparations from the ovine myometrium was saturable, of high affinity and rapidly reversed by phentolamine (10 μmol/l). Based on the relative order of potency of selected adrenergic agonists and antagonists, the myometrial binding sites labelled by [3H]prazosin and [3H]rauwolscine were characterized as α1- and α2adrenoceptors respectively. Saturation binding studies with [3H]prazosin showed that the number of α1adrenoceptors was low (maximal binding capacity, Bmax, between 19 and 24 fmol/mg protein) and there were no noticeable differences between the animal groups. Moreover, the equilibrium dissociation constant (Kd) did not vary significantly between groups (Kd between 0·10 and 0·17 nmol/l). In contrast, saturation binding studies with [3H]rauwolscine revealed the presence of a high number of α2-adrenoceptors. Values of Bmax were far higher in the pregnant ewes (1096±241 fmol/mg protein; means ± s.d.) than in any of the non-pregnant ovariectomized ewes. For these latter groups, the highest Bmax values were found in the group treated with both progestagen and oestrogen (382±77 fmol/mg protein) compared with treatment with oestrogen alone (101±8 fmol/mg protein) or with controls (82±12 fmol/mg protein). The results of the present study, especially those obtained under a high-progesterone environment (e.g. pregnancy), strongly suggest a role of steroid hormones in the control of the number of α2-adrenoceptors in the ovine myometrium. In contrast, they did not yield any supporting data for a similar role on myometrial α1-adrenoceptors in the ewe.

Journal of Endocrinology (1990) 127, 471–479
Changes in the hypothalamic contents of LHRH-I and -II and in pituitary responsiveness to synthetic chicken LHRH-I and -II during the progesterone-induced surge of LH in the laying hen
Authors: Wilson S. C. , Chairil R. A. , Cunningham F. J. , Gladwell R. T.
Published: December 2008

The contents of LHRH-I and -II in the anterior hypothalamus and posterior hypothalamus (including the mediobasal hypothalamus and median eminence) were measured at 90, 180 and 360 min after the i.m. injection of laying hens with progesterone. Whilst no changes were observed in the content of LHRH-I in the anterior hypothalamus, LHRH-I in the posterior hypothalamus tended to fall at 90 and 180 min after injection of progesterone in hens maintained on 16 h light:8 h darkness (16L:8D) and 8L:16D respectively. Pretreatment of laying hens with tamoxifen significantly increased the hypothalamic contents of LHRH-I and -II, raised the basal plasma concentration of LH and modified the LH response to progesterone injection. In hens in which tamoxifen prevented an increase in the plasma concentration of LH after progesterone injection, the content of LHRH-I in the posterior hypothalamus remained unchanged. In contrast, in hens in which progesterone stimulated a steep increase in LH within 90 min, there was a pronounced and significant fall in LHRH-I content of the posterior hypothalamus. No change in the hypothalamic content of LHRH-II was observed during the progesterone-induced surge of LH until plasma concentrations had attained maximal values or started to decline. Then, in hens maintained on 16L:8D, a significant fall in the content of LHRH-II in the anterior hypothalamus was found at both 180 and 360 min after injection with progesterone.

Tests in vitro and in vivo of the responsiveness of the pituitary gland to synthetic LHRH-I and -II revealed no change at 90 min after injection of laying hens with progesterone, when plasma concentrations of LH were increasing, but a pronounced reduction when plasma LH concentrations were maximal or falling.

These results suggest that LHRH-I mediates in the progesterone-induced increase in the plasma concentration of LH. Although the subsequent decline in plasma LH was associated with a reduced responsiveness of the pituitary gland to LHRH, a significant correlation between the contents of LHRH-I and -II in the anterior hypothalamus and a fall in the hypothalamic content of LHRH-II when plasma LH was maximal or declining allows the possibility of an involvement of this peptide in the neuroendocrine events preceding ovulation.

Journal of Endocrinology (1990) 127, 487–496
Age-related alterations in the response of hepatic lipogenic enzymes to altered thyroid states in the rat
Authors: Mooradian A. D. , Deebaj L. , Wong N. C. W.
Published: December 2008

To determine the age-related alterations in tissue-responsiveness to thyroid hormone action, the mRNA levels and the enzyme activities of hepatic cytosolic malate dehydrogenase (ME) and mitochondrial α-glycerophosphate dehydrogenase (α-GPD) were determined in groups of euthyroid, hypothyroid and hyperthyroid male Fischer 344 rats at various ages. The basal α-GPD level (change in optical density/min per mg) in 2-month-old rats (0·163 ±0·003) (s.e.m.) was significantly (P < 0·001) higher than that in 6-month-old and 26-month-old rats (0·116±0·012 and 0·098±0·013 respectively). The basal ME activity (mU/mg) was significantly (P < 0·001) reduced in aged rats (9·2±0·89) compared with younger rats (54·2±3·4 and 17·1±2·3 for 2-month-old and 6-month-old rats respectively). The response of ME to tri-iodothyronine (T3) in aged rats compared with young rats was reduced approximately 50%. This age-related reduction in ME response to T3 could not be attributed to reduced food intake with ageing. Northern blot analysis showed that ME mRNA levels in hyperthyroid aged rats were 50% of those of young hyperthyroid rats. There were no significant differences in either basal or T3-stimulated α-GPD mRNA levels. The proportional reduction in steady-state ME mRNA levels and ME activity in aged rats indicates that this age-related change is modulated at a pretranslational level.

Journal of Endocrinology (1991) 128, 79–84
Pre-exposure of rat anterior pituitary cells to somatostatin enhances subsequent growth hormone secretion
Authors: Richardson S. B. , Twente S.
Published: December 2008

The precise roles of GH-releasing factor (GRF) and somatostatin (SRIF) in the orchestration of pulsatile GH secretion have not yet been fully determined. We examined the interactions of rat GRF and SRIF, in the concentration ranges present in rat hypophysialportal blood, on the secretion of GH from dispersed male rat anterior pituitary cells in monolayer culture. The effects of exposing cells to GRF and/or SRIF (0·01–1·nmol/l) for 1 h were compared with the effects of preincubation of cells with SRIF before experimental incubations. As anticipated, the stimulatory effects of 0·1–1 nmol GRF/l were abolished by concurrent incubation with SRIF at an equimolar concentration, although SRIF, at these concentrations, did not significantly inhibit basal GH secretion. Conversely, pre-exposure to 0·1 nmol SRIF/l for 30 or 60 min, resulted in an increase in GH secretion during a subsequent 60-min incubation period, both in the absence or in the presence of GRF (0·01–1 nmol/l). Pretreatment with GRF caused increased responsivity to GRF rather than significant sensitization of the GH response to GRF.

These observations demonstrate actions of SRIF, at low and probably physiological concentrations, which are more complex than those of a pure inhibitor of GH secretion. Pre-exposure of the pituitary to SRIF enhances subsequent GH secretion, suggesting that SRIF may play an additional physiological role in amplifying the GRF signal.

Journal of Endocrinology (1991) 128, 91–95
Control of progesterone and inhibin secretion during the luteal phase in the macaque
Authors: Smith K. B. , Fraser H. M.
Published: December 2008

We investigated the temporal relationship between serum concentrations of progesterone and immuno-reactive inhibin after treatment with an LHRH antagonist ([N-Ac-d-Nal(2)1,d-pCl-Phe2,d-Trp3,d-hArg(Et2)6,d-Ala10]-LHRH), during the mid-luteal phase in the macaque. Further, in an attempt to obtain a model of transitory suppression of luteal function, the effect of treatment with the LHRH antagonist for 1, 2 or 3 days during the mid-luteal phase on serum concentrations of progesterone and immunoreactive inhibin was compared. Differences in the pattern of decline of the two hormones were observed. Progesterone concentrations fell by 6 h after antagonist administration while inhibin was not significantly suppressed until 48 h. Treatment with three injections of LHRH antagonist caused a sustained suppression of luteal function as shown by low serum concentrations of progesterone and inhibin. Recovery of progesterone and inhibin secretion was observed in two out of six macaques treated with two injections of antagonist and in three out of six treated with a single injection. Therefore, with the regimens of LHRH antagonist which we employed this approach was not conducive to obtaining a reliable transitory suppression of luteal function. To elucidate further the gonadotrophin control of inhibin, six macaques were treated with three injections of the LHRH antagonist to induce a permanent suppression of luteal function but received concomitantly either human chorionic gonadotrophin (hCG) or human FSH daily for 5 days (n = 3 per group). FSH failed to prevent the antagonist-induced fall in progesterone and inhibin while hCG treatment completely reversed the inhibitory effects of the LHRH antagonist. These results give further support to the concept that the secretion of inhibin, like progesterone, is integrated with the LH control of the corpus luteum. The slower decline in inhibin after LHRH antagonist suggests that the gonadotrophic stimulus to the corpus luteum results in a more prolonged stimulus for inhibin than for progesterone secretion, or that inhibin has a longer metabolic clearance rate.

Journal of Endocrinology (1991) 128, 107–113
Comparison of the luteolytic action of gonadotrophin-releasing hormone antagonist and cloprostenol, and the ability of human chorionic gonadotrophin and melatonin to override their luteolytic effects in the marmoset monkey
Authors: Webley G. E. , Hodges J. K. , Given A. , Hearn J. P.
Published: December 2008

The effects of the luteolytic and luteotrophic agents cloprostenol, human chorionic gonadotrophin (hCG) and melatonin on the corpus luteum have been investigated in marmoset monkeys treated with an LHRH antagonist to reduce endogenous LH secretion. This has allowed the effects of these agents to be investigated in the absence of the principal endogenous luteotrophin.

Administration of the LHRH antagonist ([N-acetyl-dβNal1-d-pCl-Phe2-d-Phe3-d-Arg6-Phe7-Arg8-d-Ala10]NH2-LHRH) or cloprostenol between days 7 and 11 after ovulation (preimplantation) resulted in luteolysis. A significant (P<0·05) decrease in progesterone concentrations had occurred by 4 h after administration of the LHRH antagonist and was indeed preceded by a fall in LH concentrations. Coadministration of hCG with the LHRH antagonist prevented the fall in progesterone. In contrast, administration of cloprostenol resulted in an immediate fall in progesterone concentrations, to less than half the initial level within 1 h, and co-administration with hCG did not prevent the fall. Administration of hCG stimulated progesterone production when given 8 h after the LHRH antagonist but not after 24 h. Cloprostenol prevented the stimulation by hCG. Co-administration of melatonin with the LHRH antagonist did not prevent the decrease in progesterone concentrations. Melatonin was also not effective in preventing the fall in progesterone induced by cloprostenol. However, co-administration of melatonin and cloprostenol between days 17 and 21 after ovulation (post-implantation) significantly (P<0·05) delayed the fall in progesterone seen with cloprostenol alone.

These results suggest that while the LHRH antagonist and cloprostenol have different sites of action their effect is similar at the corpus luteum, that is in depriving the corpus luteum of luteotrophic support. The results also suggest that melatonin may be able to influence the luteolytic action of cloprostenol but that its effect varies with the stage of the cycle. The physiological role for such an action, if any, remains unknown.

Journal of Endocrinology (1991) 128, 121–129
Discordant levels of serum bioactive LH in man as measured in different in-vitro bioassay systems using rat and mouse interstitial cells and human granulosa-luteal cells
Authors: Ding Y.-Q. , Ranta T. , Nikkanen V. , Huhtaniemi I.
Published: December 2008

Serum samples from healthy men (n = 6), perimenopausal women (n=9) and patients with polycystic ovarian disease (n = 4) were analysed for LH bioactivity by the two widely used in-vitro bioassay systems: the mouse and rat interstitial cell testosterone-formation assays. The results were compared with an assay employing LH-stimulated cyclic AMP production by cultured human granulosa-luteal cells. Average bioactive LH levels in the mouse cell assay were 1·6-fold higher than those measured using the rat assay. A good correlation (r = 0·89, P<0·01) was observed between the bioactive LH levels measured by these two assays. No significant difference was found between the sensitivities of the two assays: 0·009 ±0·003 IU/1 (mean ± s.e.m., n=10) with rat cells and 0·011±0·003 IU/1 (n=10) with mouse cells. The LH level resulting in half-maximal stimulation of testosterone production in the mouse model was twofold higher than that in the rat model (0·185 ±0.020 vs 0·083 ±0·022 IU/1, P<0·01). The bioactive LH levels measured by the human granulosa-luteal cell assay averaged 12% higher than those obtained with the rat assay (r =0·84, P<0·01), but 58% lower than levels measured with the mouse assay (r = 0·86, P<0·01). The data indicate that the target cell model used in the in-vitro bioassay of LH contributes to the documented discrepancies in reports on serum levels of bioactive LH. Although good correlations were found between all assay systems, the absolute levels of LH bioactivity measured with the rat assay are closer than mouse data to levels measured with a homologous bioassay employing human granulosa-luteal cells.

Journal of Endocrinology (1991) 128, 131–137
Characterization and localization of oxytocin receptors in the uterus and oviduct of the non-pregnant ewe using an iodinated receptor antagonist
Authors: Ayad V. J. , Guldenaar S. E. F. , Wathes D. C.
Published: December 2008

Some of the binding characteristics of a novel oxytocin receptor ligand 125I-labelled [1-(β-mercapto-β, β-cyclopentamethylene propionic acid), 2-(ortho-methyl)-Tyr2,Thr4,Orn8,Tyr9-NH2]-vasotocin ([125I]OTA) have been determined in the sheep uterus. The compound was subsequently used for the autoradiographic localization of oxytocin receptors in the uterus and oviduct of the ewe.

Specific binding of [125I]OTA to crude membrane fractions of ovine endometrium was time-dependent and was unaffected by the addition of cations to incubation media. Endometrial membranes contained a single population of saturable, high-affinity binding sites for the iodinated ligand (dissociation constant (Kd) 0·23±0·08 nmol/l) and unlabelled oxytocin competed with [125I]OTA for binding sites with high affinity (Kd 1·29±0·4 nmol/l) in the presence of Mg2+ In contrast, unlabelled OTA was able to compete with high affinity (Kd 1·13±0·16 nmol/l) in the absence of cation. Competition studies with a number of oxytocin analogues and related peptides and the tissue distribution of [125I]OTA binding sites also indicated that [125I]OTA bound to the ovine oxytocin receptor. This was further validated by autoradiographic studies which showed specific labelling with [125I]OTA to be greater to uterus and oviduct obtained from ewes which had been killed within 2 days of oestrus than to similar tissue from ewes killed during the luteal phase. In both the ampullary and isthmic regions of the oviduct and the myometrium, [125I]OTA binding sites were confined to smooth muscle. Endometrial binding sites for [125I]OTA were consistently located on the luminal epithelium and epithelial cells lining secretory glands. In addition, in one ewe which had been killed 2 days after cloprostenol treatment, stromal cells were labelled in a caruncular region of the endometrium. The consistency of this observation between similar animals remains to be determined.

The autoradiographic technique demonstrated appears sufficiently sensitive to allow further studies into the distribution of the endometrial oxytocin receptor throughout the oestrous cycle, and into its regulation at luteolysis and during the establishment of pregnancy.

Journal of Endocrinology (1991) 128, 187–195
Plasma clearance and tissue distribution of labelled insulin-like growth factor-I (IGF-I), IGF-II and des(1–3)IGF-I in rats
Authors: Ballard F. J. , Knowles S. E. , Walton P. E. , Edson K. , Owens P. C. , Mohler M. A. , Ferraiolo B. L.
Published: December 2008

Incubation of 125I-labelled insulin-like growth factor-I (IGF-I) with rat plasma at 4 °C led to the transfer of approximately half the radioactivity to 150 kDa and smaller complexes with IGF-binding proteins. The extent of association was greater with labelled IGF-II and essentially absent with the truncated IGF-I analogue, des(1–3)IGF-I. A greater degree of binding of IGF peptides with binding proteins occurred after i.v. injection of the tracers into rats, but most of the des(1–3)IGF-I radioactivity remained free. Measurement of the total plasma clearances showed the rapid removal of des(1–3)IGF-I compared with IGF-I and IGF-II; the mean clearances were 4·59, 1·20 and 1·34 ml/min per kg respectively. The mean steadystate volume of distribution was larger for des(1–3)IGF-I than for IGF-I and IGF-II (461, 167 and 181 ml/kg respectively), probably because of the differences in plasma protein binding. With all tracers, radioactivity appeared in the kidneys to a greater extent than in other organs. The amount of radioactivity found in the adrenals, brain, skin, stomach, duodenum, ileum plus jejunum and colon was in rank order, des(1–3)IGF-I > IGF-I > IGF-II. Since this ranking is the opposite of the abilities of the three IGF peptides to form complexes with plasma binding proteins, we propose that the plasma binding proteins inhibit the transfer of the growth factors to their tissue sites of action. Moreover, we suggest that IGF analogues that are cleared rapidly from blood may have greater biological potencies in vivo.

Journal of Endocrinology (1991) 128, 197–204