bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of testicular and somatic development after treatment of the postnatal rat with the Leydig cell cytotoxic ethylene dimethanesulphonate
Authors: Morris I. D. , Lendon R. G. , Zaidi A.
Published: December 2008

The Leydig cell cytotoxic ethylene dimethanesulphonate (EDS) was administered s.c. daily (50 mg/kg) to male rats aged 5–16 days. Apart from loss of weight and that the eyelids unfused earlier, no gross toxicity was observed during treatment. On day 17 testis weights, serum testosterone concentrations, testicular serum testosterone content and 125I-labelled human chorionic gonadotrophin (hCG) binding to testicular homogenates were reduced. Serum LH and FSH concentrations were elevated.

The testes did not recover from EDS treatment and at 63 and 120 days were minute (<2% of control), and the prostate and seminal vesicles were small although not completely atrophied. In addition, body weights were substantially reduced. Serum and testicular testosterone and 125I-labelled hCG binding to testicular homogenates were reduced but not absent. Serum LH and FSH concentrations were increased. Light microscopy of the adult testes showed that EDS treatment inhibited the development of the seminiferous tubules. Most of the tubules were devoid of germ cells and Sertoli cells were rare. Occasionally tubules also contained spermatogonia and spermatocytes but no signs of spermiogenesis. The testes were composed mainly of closely packed interstitial tissue with no lymphatic space. The interstitial cells resembled Leydig cells and stained for 3β-hydroxysteroid dehydrogenase. Histochemically identified Leydig cells were absent during treatment but reappeared when treatment was withdrawn. Testicular Leydig cell numbers were only 7% of control values in the 63-day-old EDS-treated rat. The effect on the testis of EDS treatment administered at a crucial time of testicular development may be explained by withdrawal of androgen; however, the systemic effects indicate non-specific toxicity so any explanation of these changes must be viewed with caution.

J. Endocr. (1988) 119, 467–474
Effect of maternal hyperglycaemia on insulin secretion by monolayer cultures of pancreatic cells from neonatal rats: a perifusion study
Authors: Takao F. , Kagawa S. , Sakamoto K. , Matsuoka A.
Published: December 2008

The effect of maternal hyperglycaemia on the function of neonatal B cells was examined using a perifusion technique in pancreatic monolayer cultures of neonatal rats from normoglycaemic mothers (C), and those made slightly hyperglycaemic (SH) and highly hyperglycaemic (HH) by injection of streptozotocin. Monolayer cultures were kept for 7 days in medium containing 5·5 mmol glucose/l plus 1 mmol 2-deoxy-glucose/l. On day 0, B cells in the C group responded to 16·7 mmol glucose/l, 10 mmol leucine/l and 10 mmol 2-ketoisocaproate/l in a monophasic fashion with no significant rise in the second phase. However, compared with the C group, a significant increase in the second-phase secretion in response to glucose and 2-ketoisocaproate was observed in the SH group, although there was no difference in the first-phase secretion. In the HH group the insulin secretion was lower in the first phase but not in the second phase. After culture for 7 days, B cells in the C group showed a biphasic response to the secretagogues, with a great increase in the second-phase secretion. In the SH group, the second phase of insulin secretion was increased but the increment was far less than that in the C group. The secretory response was remarkably low in the HH group compared with other groups. From these results, we conclude that at an early stage of culture slight maternal hyperglycaemia causes a hypersensitivity of neonatal B cells but impairs the normal development of the function of B cells during culture, and that high hyperglycaemia results in impaired insulin secretion throughout the whole period of culture studied.

J. Endocr. (1988) 119, 493–499
Effects of morphine and naloxone on plasma levels of LH, FSH, prolactin and growth hormone in the immature male pig
Authors: Trudeau V. L. , Meijer J. C. , van de Wiel D. F. M. , Bevers M. M. , Erkens J. H. F.
Published: December 2008

The effects of acute i.v. administration of gonadotrophin-releasing hormone (GnRH; 0·1 μg/kg), morphine (3 mg/kg) and/or naloxone (0·5 mg/kg) on LH and FSH secretion was evaluated in young male pigs (approximately 6 weeks old) with venous brachiocephalic cannulae. The effects of morphine and/or naloxone treatments on prolactin and GH were also evaluated. The influence of morphine on hypophysial hormone secretion was also examined 2 days after castration. Animals treated with morphine and/or naloxone were compared with saline-injected control animals. Injection of GnRH induced 400 and 50% increases in LH and FSH respectively. Morphine and/or naloxone did not influence LH secretion in intact or castrated animals. Morphine suppressed (P < 0·01) FSH levels 40–60 min after injection whereas naloxone had no effect. Castration eliminated morphine-induced suppression of FSH. Injection of morphine followed by naloxone resulted in acutely raised (P < 0·05) FSH concentrations. Morphine induced a threefold increase (P < 0·01) in prolactin within 30 min of injection and naloxone inhibited the effect of morphine. Levels of GH were increased (P < 0·01) 20 min after morphine treatment and this increase was delayed when naloxone was given immediately after morphine. Naloxone alone did not affect prolactin or GH secretion. Castration caused increases in LH (P < 0·05) and FSH (P < 0·01), did not influence prolactin or GH, and reduced plasma testosterone to undetectable (< 1·0 nmol/l) levels. These results suggest that in young male pigs the hypothalamic-hypophysial axis is responsive to GnRH and gonadal negative feedback. The opiate/LH pathway appears to be non-functional or incomplete, while the opiate/FSH pathway seems to be active. Morphine stimulated the release of prolactin probably via a naloxone-sensitive opiate receptor.

J. Endocr. (1988) 119, 501–508
Effect of α-melanocyte-stimulating hormone on tyrosinase activity in hair follicular and epidermal melanocytes of the mouse
Authors: Seechurn P. , Burchill S. A. , Thody A. J.
Published: December 2008

In this study, the effect of α-MSH on tyrosinase activity was compared in epidermal and hair follicular melanocytes of mice. It had no effect on epidermal tyrosinase activity in dorsal skin from neonatal non-agouti black mice (C57BL/6J) in both in-vivo and in-vitro experiments. Theophylline and 8-bromocyclic (c)AMP were similarly without effect in in-vitro experiments. In-vivo administration of α-MSH and theophylline for 7 days was also without effect on epidermal tyrosinase activity in ear skin of adult non-agouti mice, and the same was true for α-MSH in wild-type agouti mice. Activation of the epidermal melanocytes in the non-agouti and wild-type agouti mice with ultraviolet radiation also failed to bring about a response to α-MSH and to theophylline in the case of the former. No tyrosinase activity was detected in the epidermis of viable yellow mice (C3H-HeAvy), but, as shown previously, tyrosinase activity was present in the hair follicle when the hair was actively growing and was increased in those mice given either α-MSH or theophylline. α-MSH and theophylline had no such effects on hair follicular tyrosinase activity in the non-agouti mice.

The present results suggest that α-MSH- and cAMP-dependent mechanisms have little or no importance in the regulation of tyrosinase expression in mouse epidermal melanocytes. α-MSH may, however, regulate tyrosinase expression in hair follicular melanocytes, but even in these melanocytes its action may be restricted to mice that express the agouti gene.

J. Endocr. (1988) 119, 517–522
DEMONSTRATION OF MELATONIN-BINDING SITES ON THE PARS TUBERALIS OF THE RAT
Authors: Williams L. M. , Morgan P. J.
Published: December 2008

Melatonin-binding sites have previously been identified in the suprachiasmatic nucleus (SCN) and median eminence (ME) of the rat. We have further investigated the localization of melatonin-binding sites in the rat hypothalamus and pituitary using the ligand [125I] iodomelatonin and in-vitro autoradiography. The presence of specific melatonin-binding sites in the SCN is confirmed; however the second area of melatonin binding is identified as the pars tuberalis of the pituitary and not the ME as previously described. No other areas which bound melatonin were found in either the pituitary or the hypothalamus.
Thyrotrophin-releasing hormone-related polypeptides in rabbit prostate and semen are different from those in rabbit hypothalamus
Authors: Cockle S. M. , Morrell J. M. , Smyth D. G.
Published: December 2008

TRH-related peptides were extracted from the hypothalamus and prostate gland of the rabbit. The peptides were fractionated by gel exclusion chromatography and located by trypsin digestion and radioimmunoassay with antibodies to TRH amide and TRH–Gly Lys. In the hypothalamus TRH-related peptides containing approximately 16 and 30 residues were observed: in these peptides the extensions to the TRH sequence were exclusively in the C-terminal direction. In addition, the three-residue form of TRH was also present. In the prostate complex, the predominant TRH-related peptide contained approximately 50 residues and the extension to the TRH tripeptide was on the N-terminal side; a three-residue form of immunoreactive TRH was also demonstrated. The same pattern of TRH-related peptides was shown to be present in rabbit semen. The results reveal the existence of a novel TRH-related polypeptide in the prostate and semen which does not occur in the hypothalamus. This peptide appears to undergo secretion.

Journal of Endocrinology (1989) 120, 31–36
Oestrogen receptors and effects of oestradiol administration on mRNA synthesis in the limbic system of the neonatal female rat
Authors: Greenstein B. D. , Adcock I. M.
Published: December 2008

There is sexual dimorphism of specific species of mRNA in the neonatal rat brain and this sexual dimorphism may be imprinted by steroids of testicular origin during the perinatal period. According to current theories, only aromatizable androgens may cause sexual differentiation of sexual behaviour and function in the adult. The effects of oestradiol benzoate on mRNA synthesis in the neonatal female limbic system were therefore studied. In addition, cytosolic and nuclear oestrogen receptors were measured after administration of testosterone propionate, oestradiol benzoate or dihydrotestosterone (DHT). An attempt was made to distinguish between the brain oestrogen receptor and the plasma oestrogen-binding protein, alphafoetoprotein (AFP) by isoelectric focussing. After injection of 50 μg oestradiol benzoate s.c. to neonatal female rats, the expression of mRNA coding for sexually dimorphic proteins appeared to be changed to a male-type pattern. The overall density of labelling was noticeably greater and specific changes in labelled proteins were observed. These effects were observed within 3 h of injection. Both testosterone and oestradiol caused a marked depletion of cytosolic oestrogen receptors in the limbic system whereas DHT was ineffective in this respect. Nuclear receptors were present in equal abundance in male- and female-derived nuclei and only oestradiol was able to cause a significant (P < 0·025) increase in nuclear oestrogen receptors. The receptor and AFP could be distinguished by isoelectric focussing, since the pI of the receptor was 7·05, while that of AFP was 4·5. These results are consistent with the possibility that oestradiol alters transcription in the neonatal rat brain and may do this through the oestrogen receptor. Nevertheless, it is also possible that oestradiol could alter post-transcriptional events such as the stability of mRNA or the binding of tRNA to the polysomal complex.

Journal of Endocrinology (1989) 120, 83–88
Growth hormone regulates the level of insulin-like growth factor-I mRNA in rat skeletal muscle
Authors: Isgaard J. , Nilsson A. , Vikman K. , Isaksson O. G. P.
Published: December 2008

Levels of mRNA for the insulin-like growth factor-I (IGF-I) in rat heart and skeletal muscle and its dependence on GH were investigated using a solution hybridization assay. Levels of IGF-I mRNA decreased following hypophysectomy, and replacement therapy with human GH (hGH) normalized heart and skeletal muscle levels. The stimulatory effect of hGH was dose-dependent, the lowest effective dose being 100 μg. A significant increase of IGF-I mRNA was observed 60 min after s.c. administration of 100 μg hGH and the maximum increase was apparent 6–12 h after hGH injection. Administration of 200 μg IGF-I or 11 μg insulin did not significantly change levels of IGF-I mRNA. The results show that GH regulates the level of IGF-I mRNA in rat heart and skeletal muscle and give further support to the hypothesis that locally produced IGF-I might be a local mediator for the direct stimulatory effect of GH on the growth and development of heart and skeletal muscle.

Journal of Endocrinology (1989) 120, 107–112
Stress alters immune function and disease resistance in chinook salmon (Oncorhynchus tshawytscha)
Authors: Maule A. G. , Tripp R. A. , Kaattari S. L. , Schreck C. B.
Published: December 2008

We examined the effects of acute stress on the immune system and disease resistance of juvenile chinook salmon (Oncorhynchus tshawytscha) in laboratory and clinical trials. Immune function, as measured by the ability of lymphocytes from the anterior kidney to generate specific antibody-producing cells (APC) in vitro, was depressed 4 h after stress, when plasma cortisol levels were highest. At the same time, resistance to the fish pathogen, Vibrio anguillarum, was also depressed. Compared with controls, plasma cortisol and APC of stressed fish were unchanged after 24 h, and disease resistance was enhanced as evidenced by higher survival rate and longer mean time to death of mortalities. After 7 days, even though numbers of APC were depressed, plasma cortisol concentration and disease resistance did not differ from controls. This pattern was generally the same, independent of the type of stress applied: i.e. being held out of water in a dipnet for 30 s, manipulation during hatchery operations for 4 h, or transportation for 9 h. These and earlier findings suggest that similar endocrine-immune interactions operate in the mammalian and salmonid systems during acute stress.

Journal of Endocrinology (1989) 120, 135–142
Stimulation of ornithine decarboxylase activity by arginine vasopressin in the rat medullary thick ascending limb of Henle's loop
Authors: Charlton J. A. , Baylis P. H.
Published: December 2008

The effect of arginine vasopressin (AVP) on rat renal ornithine decarboxylase (ODC) activity was investigated by a cytochemical technique optimized for use in the medullary thick ascending limb of Henle's loop (mTAL). Stimulation of ODC activity by AVP was confined to the mTAL. Peaks in enzyme activity in cultured rat renal segments occurred after tissue had been exposed to AVP for 3 or 8 min and these times of maximal stimulation did not change with the concentration of AVP. There was a dose-dependent response in ODC activity over the AVP concentration range 0·01–10 fmol/l. The ODC response to AVP was totally blocked by specific antiserum to AVP and reduced by 70% with the specific inhibitor to ODC, difluoromethyl ornithine.

Journal of Endocrinology (1989) 120, 195–199
Characterization of specific insulin-like growth factor (IGF)-I and IGF-II receptors on cultured rabbit articular chondrocyte membranes
Authors: Jansen J. , van Buul-Offers S. C. , Hoogerbrugge C. M. , de Poorter T. L. , Corvol M. T. , Van den Brande J. L.
Published: December 2008

The interaction of insulin-like growth factor (IGF)-I and IGF-II with specific type-I and -II receptor sites on rabbit articular chondrocyte membranes was studied. With labelled IGF-I as tracer, half-maximal displacement of the label was obtained with 1·4 ng IGF-I/ml and 22 ng IGF-II/ml. Using IGF-II as labelled peptide, 16 ng unlabelled IGF-II/ml and 200 ng IGF-I/ml were needed to inhibit the binding by 50%. Covalent cross-linking experiments revealed the presence of typical type-I (Mr 130 000 under reducing conditions) and type-II (Mr 260 000) receptor sites. In addition, with 125I-labelled IGF-II a very intense labelled band appeared at Mr > 300 000. This band was not found in mouse liver membranes and human placental membranes.

Journal of Endocrinology (1989) 120, 245–249
Effects of neonatal androgenization on growth and carcass composition in female mice
Authors: Ventanas J. , López-Bote C. J. , García C. , Gázquez A. , Burgos J.
Published: December 2008

Sixty female mice were injected neonatally with testosterone propionate. This led to an increase in body weight at 56 days (P<0.01) and a reduction in carcass fat (P<0.005). Food conversion ratio from 28 to 49 days was lower in the treated group than in the controls (P<0.01). The data indicate that treated females can reach values similar to those of males.

Histological studies revealed a lack of luteal tissue in treated females at 56 days. This effect might be due to a modification in the nervous control of ovarian activity. Growth hormone secretion was higher in treated females than in controls (P<0-05). These results suggest that androgenization of females to achieve the performance characteristics of intact males could have important implications in meat production.

Journal of Endocrinology (1989) 120, 281–285
Changes in the plasma concentrations of inhibin throughout the normal sheep oestrous cycle and after the infusion of FSH
Authors: McNeilly A. S. , Swanston I. A. , Crow W. , Tsonis C. G. , Baird D. T.
Published: December 2008

A radioimmunoassay for inhibin was developed using a peptide containing the 1–26 amino acid sequence of the N-terminus of the α-chain of 32 kDa porcine inhibin as immunogen, and 125I-labelled tracer. Evaluation of this assay using Sephadex column chromatography, chromatoelectrophoresis and immunoblotting confirmed that it measured all forms of inhibin present in sheep follicular fluid and was suitable for measurement of inhibin in sheep plasma. There was no evidence of the presence of free α-subunit in either sheep follicular fluid or ovarian vein plasma.

The concentration of inhibin in jugular plasma throughout the follicular and luteal phases of four ewes with ovarian autotransplants was measured. The ovarian secretion of inhibin and oestradiol were also measured simultaneously throughout the follicular phase in a spontaneous cycle and after infusion of NIH-oFSH-S14 at 10 μg/h for 48 h following premature luteal regression induced by prostaglandin. The results showed: (1) no change in the peripheral concentration of inhibin throughout the cycle except an increase related to the periovulatory increase in FSH and LH. (2) Following luteal regression, the concentration of FSH fell as the secretion rate of oestradiol increased. During this time there was no significant change in the peripheral concentration of inhibin or ovarian inhibin secretion rate. (3) Following the infusion of FSH there was a marked increase in the concentration of inhibin in both ovarian and peripheral plasma and an increase in ovarian inhibin secretion rate. (4) The calculated metabolic clearance rate of inhibin, 20·3 ml/min, is similar to that of FSH.

We conclude that in the ewe the ovarian inhibin secretion rate is stimulated by FSH and, although inhibin may modulate the basal secretion of FSH, a change in its secretion does not account for the fall in FSH which occurs during the follicular phase of the sheep oestrous cycle.

Journal of Endocrinology (1989) 120, 295–305
Human 'pregnancy-associated endometrial α1-globulin', an insulin-like growth factor-binding protein: immunohistological localization in the decidua and placenta during pregnancy employing monoclonal antibodies
Authors: Waites G. T. , James R. F. L. , Bell S. C.
Published: December 2008

We have previously shown that pregnancy-associated endometrial α1-globulin, a small molecular weight insulin-like growth factor-binding protein (IGF-BP), is quantitatively the major secretory protein product of the decidualized endometrium during human pregnancy. In the present study, employing monoclonal antibodies raised against this protein in an immunohistological technique, the cellular localization of the protein has been examined in the decidua and placenta during pregnancy. During the first trimester the protein was principally associated with the decidual cell in the decidualized decidua compacta region of the endometrium with both cytoplasmic and extracellular matrix-associated staining patterns being detected. No extensive staining was observed in the placenta. At term the protein was localized in similar cells in the placental bed and endometrium associated with the amniochorion but not in the placenta. These studies suggest that the decidual cell represents the major source of IGF-BP during pregnancy and have relevance to the origin of amniotic fluid IGF-BP and the paracrine role of the decidual cell in the control of trophoblast growth.

Journal of Endocrinology (1989) 120, 351–357
An enzyme-linked immunosorbent assay to study human relaxin in human pregnancy and in pregnant rhesus monkeys
Authors: Lucas C. , Bald L. N. , Martin M. C. , Jaffe R. B. , Drolet D. W. , Mora-Worms M. , Bennett G. , Chen A. B. , Johnston P. D.
Published: December 2008

A sensitive and specific double-antibody enzyme-linked immunoassay, using a synthetic analogue of human relaxin for standard and immunogen, was developed for the measurement of human relaxin (hRLX) in serum and plasma. No cross-reactivity was observed for human insulin, human insulin-like growth factor-I, hGH, human chorionic gonadotropin, hFSH, hLH or human prolactin. The assay was used to monitor RLX concentrations in samples from men, non-pregnant and pregnant women, and in pregnant rhesus monkeys infused with hRLX. RLX was not detected in serum from men nor from non-pregnant women, while a concentration of 600 ng/l was measured in pooled sera from two pregnant women (pregnancies achieved by in-vitro fertilization). Immunoreactive RLX (1·1 μg/g) was found in human corpora lutea taken from ectopic pregnancies at 7 weeks. In an experiment with a pregnant rhesus monkey infused with human RLX analogue, less than 1·5% of the maternal concentration was measured in the fetal circulation. Even though preliminary, these data suggest a low level of transfer of human analogue relaxin across the placenta in a rhesus monkey. Further studies of the physiology of RLX in human pregnancy will be facilitated by the availability of this immunoassay.

Journal of Endocrinology (1989) 120, 449–457
Rate of reproductive involution following either exposure to short days or daily administration of melatonin is faster in inbred than in random-bred female Syrian hamsters
Authors: Reiter R. J. , Sabry I. , Nordio M. , Vaughan M. K. , Migliaccio S.
Published: December 2008

The onset of cessation of oestrous cyclicity and associated organ and hormonal changes were compared in random-bred (RB) and inbred (IB) female Syrian hamsters kept either under short days (8 h light:16 h darkness; 8L:16D) or long days (14L:10D) and given daily afternoon injections of 25 μg melatonin. In response to short-day treatment, 100% of the IB hamsters exhibited vaginal acyclicity within 35 days; by comparison, none of the RB animals were acyclic at this time. The IB hamsters also exhibited other changes associated with exposure to short days, including increased body weight, enlarged ovaries, regressed uteri, elevated pituitary concentrations of FSH, and depressed pituitary and plasma concentrations of prolactin. At this time, only the pituitary FSH levels were increased in the RB animals kept under the same short-day conditions.

In a second experiment, RB and IB female Syrian hamsters were maintained under long days (14L:10D) and the rate of reproductive regression in response to daily afternoon injections of melatonin was compared. After 8 weeks of melatonin injections, 80% of the IB females were anoestrous, while all RB hamsters were still exhibiting 4-day oestrous cycles. Other changes associated with melatonin administration in the IB females included a marked drop in uterine weight and a depression in pituitary and plasma prolactin levels. The RB hamsters, although they were all still cyclic after 8 weeks, had increased body and ovarian weights, increased pituitary concentrations of FSH, and lower pituitary and plasma prolactin levels.

The results show that the IB strain of Syrian hamster, compared with the RB strain, responded more quickly with vaginal acyclicity to both exposure to short days and daily injections of melatonin. On the other hand, the IB hamsters responded more slowly in terms of oestrous acyclicity to melatonin injections than to treatment with short photoperiod.

Journal of Endocrinology (1989) 120, 489–496
Inhibitory effects of corticotrophin-releasing factor and β-endorphin on LH and FSH secretion in the lactating rat
Authors: Taya K. , Sasamoto S.
Published: December 2008

The roles of corticotrophin-releasing factor (CRF) and β-endorphin in the suppression of LH and FSH secretion during lactation were investigated using ovariectomized lactating rats separated from their litters overnight. Within 1 h of returning the pups to their mothers a marked fall in plasma LH concentration and a large increase in plasma prolactin were noted. However, resuckling caused no significant change in plasma concentration of FSH until 12 h after the return of the litter but a significant decline occurred thereafter. Twenty-four hours after removal of the litter, a single i.v. injection of 200 μl anti-LHRH serum caused similar changes in plasma concentrations of LH and FSH observed in nursing rats during suckling. These results suggest that the suckling stimulus itself is responsible for the suppression of LH as well as FSH, via inhibition of the secretion of LHRH. Twenty-four hours after removal of the litter, a single intracerebroventricular (i.c.v.) injection of either 10 μg CRF or β-endorphin resulted in a rapid decrease in plasma LH. Only β-endorphin caused a marked increase in plasma levels of prolactin within 1 h whereas FSH was less affected by either hormone. Repeated i.c.v. administration of 10 μg CRF or β-endorphin at 6-h intervals caused a prolonged inhibition of LH as well as FSH secretion during 48 h, with β-endorphin being less effective than CRF.

These results demonstrate that the suckling stimulus alone suppressed the secretion of both LH and FSH, and suggest that this effect may be mediated by the inhibition of LHRH secretion from the hypothalamus. They also suggest that the suckling-induced inhibition of LHRH may be primarily mediated by endogenous CRF and opioid peptides.

Journal of Endocrinology (1989) 120, 509–515
POTENTIATION OF GROWTH HORMONE ACTIVITY IN SHEEP USING MCNCCLCNAL ANTIBODIES
Authors: Pell J.M. , Johnsson I.D. , Pullar R.A. , Morrell D.J. , Hart I.C. , Holder A.T. , Aston R.
Published: December 2008

Monoclonal antibody CAll was raised against ovine GH; its effects on GH activity were examined in a target species relevant for animal production in vivo. The monoclonal antibody was found to enhance the galactopoietic response to exogenous GH in adult lactating ewes and also to potentiate the diabetogenic activity of both exogenous and endogenous GH in ewe lambs. Thus it was shown that GH activity may be manipulated above its usual dose-response range in normal, intact animals of commercial importance via immunological means.
In-vivo uptake of human growth hormone in male rat liver
Authors: Bullier-Picard F. , Postel-Vinay M. C. , Kayser C.
Published: December 2008

125I-Labelled human GH (hGH) was injected i.v. to male rats and its subcellular distribution in the hepatocyte was examined using fractionation techniques. Uptake into liver homogenates was maximal by 15 min after injection and represented 24% of the injected radioactivity; it was markedly inhibited by coinjection of native hGH. 125I-Labelled hGH taken up by the liver underwent a time-dependent translocation process. The peak of specific labelling of plasma membranes occurred at 3 min whereas later on the radioactivity was concentrated in low-density structures present in Golgi-endosome fractions. To characterize the ligand-associated structures better, endosome-enriched fractions were prepared from a microsomal fraction by isopycnic centrifugation in a sucrose gradient and a Nycodenz gradient. The radioactivity was in one peak with a median density of 1·096 g/cm3 in the Nycodenz gradient fractions. The peak of radioactivity was distinct from that of galactosyltransferase activity which appeared at a median density of 1·114 g/cm3. The labelled material eluted from the various subcellular fractions appeared as intact hGH.

Upon in-vivo interaction with male rat hepatocytes, 125I-labelled hGH was internalized with a sequential association with plasma membranes and endocytic structures distinct from Golgi elements.

Journal of Endocrinology (1989) 121, 19–25
Effects of hypothyroidism, tri-iodothyronine and glucocorticoids on growth hormone responses to growth hormone-releasing hormone and His-d-Trp-Ala-Trp-d-Phe-Lys-NH2
Authors: Edwards C. A. , Dieguez C. , Scanlon M. F.
Published: December 2008

The aim of this study was to investigate the role of thyroid hormones and glucocorticoids on GH secretion. Secretion of GH in response to GH-releasing hormone (GHRH) (5 μg/kg) was markedly (P < 0·001) decreased in hypothyroid rats in vivo (peak GH responses to GHRH, 635 ± 88 μg/l in euthyroid rats vs 46 ±15 μg/l in hypothyroid rats). Following treatment with tri-iodothyronine (T3; 20 μg/day s.c. daily for 2 weeks) or cortisol (100 pg/day s.c. for 2 weeks) or T3 plus cortisol, a marked (P <0·01) increase in GH responses to GHRH was observed in hypothyroid rats (peak GH responses, 326 ±29 μg/l after T3 vs 133+19 μg/l after cortisol vs 283 ± 35 μg/l after cortisol plus T3). In contrast, none of these treatments modified GH responses to GHRH in euthyroid animals. Hypothyroidism was also associated with impaired GH responses to the GH secretagogue, Hisd-Trp-Ala-Trp-d-Phe-Lys-NH2 (GHRP-6). Secretion of GH in response to GHRP-6 in vivo was reduced (P <0·01) in hypothyroid rats (peak GH responses, 508 ± 177 μg/l in euthyroid rats vs 203 ± 15 μg/l in hypothyroid rats). In-vitro studies carried out using monolayer cultures of rat anterior pituitary cells derived from euthyroid and hypothyroid rats showed a marked impairment of somatotroph responsiveness to both GHRP-6 and somatostatin in cultures derived from hypothyroid rats. In summary, our data suggest that thyroid hormones and glucocorticoids influence GH secretion by modulating somatotroph responsiveness to different GH secretagogues.

Journal of Endocrinology (1989) 121, 31–36
Characterization and localization of receptors for epidermal growth factor in ovine skin
Authors: Wynn P. C. , Maddocks I. G. , Moore G. P. M. , Panaretto B. A. , Djura P. , Ward W. G. , Fleck E. , Chapman R. E.
Published: December 2008

Specific receptor sites for murine epidermal growth factor (EGF) have been characterized and their distribution determined in ovine skin. Binding of 125I-labelled EGF to skin membrane particles was temperature- and time-dependent, with equilibrium being reached within 1 h at 23 °C. Analysis of skin biopsies collected from ten castrated Merino sheep demonstrated the presence of a single class of saturable, high-affinity binding sites with a dissociation constant of 64 ± 4 (s.e.m.) pmol/l and a binding capacity of 33·8 ± 4·5 fmol/mg protein. Skin particle binding of 125I-labelled EGF was inhibited equipotently by mouse salivary gland EGF, EGF produced by recombinant DNA procedures and urogastrone. The EGF peptides 1–48, 6–53 and 7–53, derived from the native molecule by enzymatic cleavage, were much less potent. The relative binding potency of these molecules was correlated with their ability to induce precocious eyelid opening in mice and to inhibit wool follicle activity. Synthetic fragments representing the major structural domains of the EGF molecule (EGF(29–44), EGF(33–42) and EGF(3–31)) were inactive in both the receptor and bioassays. Auto-radiography of skin sections incubated with 125I-labelled EGF in vitro or of sections from skin which was perfused with 125I-labelled EGF in vivo demonstrated that EGF receptors were localized in undifferentiated cells of the epidermis and sebaceous glands, the inner and outer root sheath and bulb of wool follicles and in dermal arterioles. Differences in receptor concentration were observed between follicles following in-vivo perfusion of 125I-labelled EGF but not when the in-vitro labelling technique was used. The presence of receptors in these regions is consistent with the morphological changes in sheep skin in reponse to EGF administration which have been reported previously.

Journal of Endocrinology (1989) 121, 81–90
Concentrations of dopamine and noradrenaline in hypophysial portal blood in the sheep and the rat
Authors: Thomas G. B. , Cummins J. T. , Smythe G. A. , Gleeson R. M. , Dow R. C. , Fink G. , Clarke I. J.
Published: December 2008

The concentrations of dopamine, noradrenaline and their respective primary neuronal metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylethyleneglycol (DHPG) were measured in the hypophysial portal and peripheral plasma of sheep and rats by combined gas chromatography–mass spectrometry. Hypophysial portal and jugular blood samples were taken at 5- to 10-min intervals for 3–7 h from six conscious ovariectomized ewes. Blood was also collected for 30 min under urethane anaesthesia from the cut pituitary stalk from 16 pro-oestrous female and five intact male rats.

In ovariectomized ewes, noradrenaline concentrations were higher in hypophysial portal plasma than in peripheral plasma (6·6 ± 0·8 vs 2·2 ± 0·4 nmol/l). In contrast, dopamine was undetectable (<1 nmol/l) in the portal and peripheral plasma of all ewes. Plasma levels of DOPAC and DHPG in portal and jugular samples were similar. In all pro-oestrous female rats, plasma concentrations of dopamine were higher in portal blood than in jugular blood (8·0±1·4 vs 4·8± 0·6 nmol/l). Detectable concentrations of dopamine were measured in the portal plasma of two out of five male rats. Noradrenaline concentrations were higher in portal plasma than in peripheral plasma of both female (8·3 ± 1·7 vs 3·7 ± 0·6 nmol/l) and male (14·8± 2·7 vs 6·1± 1·2 nmol/l) rats.

These data show that noradrenaline, but not dopamine, is secreted into the long portal vessels in sheep. The results suggest that there are species differences in the secretion of hypothalamic dopamine into hypophysial portal blood.

Journal of Endocrinology (1989) 121, 141–147
Effects of selective opioid-receptor blockade on the hypothalamo-pituitary-adrenocortical responses to surgical trauma in the rat
Authors: Cover P. O. , Buckingham J. C.
Published: December 2008

Opioid substances have been shown to stimulate and depress the secretion of ACTH in the rat. Their opposing actions appear to be mediated in part by specific receptors in the hypothalamus which influence the secretion of corticotrophin-releasing factor (CRF). In an attempt to determine the physiological role of these receptor systems, experiments were carried out in which the plasma ACTH and serum corticosterone concentrations were determined before and after stress in rats treated s.c. with selective antagonists of μ-(naloxone, naltrexone), δ-(ICI 174864) and κ-(MR2266) opioid receptors. Neither naloxone (25–100 μg/100 g) nor naltrexone (50 μg/100 g) influenced the resting plasma ACTH or serum corticosterone concentrations. However, both inhibited (P < 0·01) the secretion of the two hormones elicited normally by surgical stress (laparotomy under ether anaesthesia). ICI 174864 (30–100 μg/100 g) also had little effect on resting hypothalamo-pituitary-adrenocortical (HPA) activity but, at the highest dose, it caused a small (P < 0·05) potentiation of the response to surgery. In contrast, MR2266 (150–300 μg/100 g) produced marked activation of the HPA system and not only stimulated the resting secretion of ACTH and corticosterone but also potentiated and prolonged the HPA response to stress.

The results suggest that μ- and κ-opioid receptors mediate opposing actions of endogenous opioid peptides, both of which may be physiologically important in the regulation of CRF release.

Journal of Endocrinology (1989) 121, 213–220
Cyclical changes in plasma renin during the oestrous cycle in the rat: synchronized effect of oestrogen and progesterone
Authors: De Vito E. , Guardia D. C. , Cabrera R. R.
Published: December 2008

The aim of the present work was to study the relationship between sex hormones and plasma renin levels during the oestrous cycle in a Wistar-derived rat strain. Plasma renin activity (PRA) as well as plasma renin concentration (PRC) were increased during the day of oestrus in rats with controlled 4-day oestrous cycles. This increase in PRA and PRC was not found when rats were ovariectomized on dioestrus day 2 and samples measured on the expected day of oestrus. The increase in PRA and PRC was not found when normal cyclic rats were treated with either tamoxifen or the progesterone receptor blocker RU 38486. Treatment with progesterone at pro-oestrus after ovariectomy on dioestrus day 2 partially increased the PRA and PRC when compared with the values found during the day of oestrus in control rats. The combined treatment of ovariectomized rats on dioestrus day 2 with oestrogen and progesterone restored the normal increase in PRA and PRC values on the expected day of oestrus. We therefore postulate that the sodium diuresis promoted by progesterone may be modulated by the previous peak of oestrogen. However, stimulation of extrarenal sources of renin cannot be excluded nor can an involvement of inactive precursors of renin in the fluctuations of active renin that occur during the oestrous cycle. No important change in plasma renin substrate (PRC) was observed during the oestrous cycle. PRA, PRC and PRS were determined every 4 h during the 4-day oestrous cycle. Our results clearly show a rhythmic variation in PRA and PRC which increases during the day of oestrus with a peak at 06.00 h. No circadian variation related to the sleep-wakefulness rhythm or other regular daily changes in PRA, PRC or PRS was found.

Journal of Endocrinology (1989) 121, 261–267
The regulation by thyroid hormones and androgen of epidermal growth factor synthesis in the submandibular gland and its plasma concentrations in mice
Authors: Kasayama S. , Yoshimura M. , Oka T.
Published: December 2008

The effects of androgen and thyroid hormones on epidermal growth factor (EGF) synthesis in the submandibular gland and on plasma EGF concentrations in mice were examined. Testosterone propionate was administered alone or in combination with l-thyroxine (T4) to female mice for 2 weeks. The submandibular EGF concentrations were increased by the administration of testosterone propionate in a dose-dependent fashion; the maximal increase, 20-fold, being produced by a dose of 2 mg every other day. The EGF levels were increased sevenfold by T4, which also enhanced the stimulatory effect of suboptimal doses of testosterone propionate. Cyproterone acetate, an anti-androgen, inhibited the testosterone propionate-induced increase, but not the T4-induced increase. Plasma EGF concentrations were raised by testosterone propionate but not by T4. Both hormones stimulated the accumulation of 4·7 kb preproEGF mRNA in the submandibular gland, which occurred almost in a parallel manner with the increase in submandibular EGF concentrations. These results suggest that EGF synthesis in the submandibular gland is regulated by alterations in the level of its mRNA by thyroid hormones and androgen, and that the rise in plasma EGF concentrations is under the influence of androgen but not of thyroid hormones.

Journal of Endocrinology (1989) 121, 269–275
A new way to induce oestrogen-deficiency osteopaenia in the rat: comparison of the effects of surgical ovariectomy and administration of the LHRH agonist buserelin on bone resorption and composition
Authors: Goulding A. , Gold E.
Published: December 2008

Prolonged administration of LHRH agonist suppresses pituitary gonadotrophin secretion, thereby lowering blood oestrogen. This study was undertaken to compare the osteopaenic effects of bilateral ovariectomy and chronic administration of the LHRH agonist, buserelin, in the rat. Four groups of animals which had their skeletons labelled with 45Ca were studied for 4 weeks. Group 1 underwent a sham-ovariectomy, group 2 were surgically ovariectomized, group 3 were given buserelin by daily s.c. injection and group 4 were given a continuous infusion of buserelin by osmotic minipump. Plasma concentrations of oestradiol were measured weekly. Bone resorption was assessed by measuring the urinary excretion of 45Ca and hydroxyproline and determining bone 45Ca content.

Ovariectomy and buserelin treatments lowered blood oestradiol, increased biochemical indices of bone resorption and decreased femur and total body calcium and 45Ca values. The degree of oesteopaenia elicited by ovariectomy and buserelin treatment was similar. Bone responses to s.c. buserelin and to continuous buserelin infusion were alike. We attribute evidence of increases in bone resorption and induction of osteopaenia with buserelin treatment to hypo-oestrogenism.

We have shown for the first time by bone analysis that buserelin induces osteopaenia as effectively as bilateral ovariectomy. This appears to be the first demonstration in the rat that long-term administration of LHRH agonist influences bone. Administration of buserelin provides a new way of inducing oestrogen-deficiency osteopaenia in the rat without removing the ovaries.

Journal of Endocrinology (1989) 121, 293–298
Effect of level of food intake of ewes on the secretion of LH and FSH and on the pituitary response to gonadotrophin-releasing hormone in ovariectomized ewes
Authors: Rhind S. M. , Martin G. B. , McMillen S. , Tsonis C. G. , McNeilly A. S.
Published: December 2008

The effect of level of food intake on LH and FSH profiles and pituitary sensitivity to gonadotrophin-releasing hormone (GnRH) was investigated in two groups of 12 ovariectomized ewes. Ewes with a high intake (group H) had a mean daily intake (± s.e.m.) of 1·99 ± 0·075 kg dry matter (DM)/head per day while ewes with a moderate intake (group M) consumed a mean of 1·02 ± 0·021 kg DM/head per day. Ovaries were surgically removed from six ewes of each group on day 11 of the luteal phase and from the remainder 30 h after an injection of 100 μg prostaglandin analogue given on day 11 to induce luteolysis. During both the luteal phase and the follicular phase, mean LH and FSH concentrations and LH pulse frequencies and amplitudes were unaffected by the level of intake but mean plasma prolactin concentrations were higher (P < 0·05) in group H than in group M ewes in the follicular phase. Mean LH and FSH concentrations at day 2 after ovariectomy were unaffected by treatment while mean prolactin concentrations were higher (P < 0·05) in group H than in group M ewes. At day 7 after ovariectomy, mean LH and FSH concentrations were lower (P < 0·05) in group H than in group M ewes although mean LH pulse frequencies and pulse amplitudes were not significantly affected by the level of intake at either time.

The level of food intake and the stage of the oestrous cycle at the time of ovariectomy did not affect the amount of LH released in response to a bolus injection of GnRH (10 μg, i.v.) but the FSH response was significantly (P < 0·05) greater in group M than in group H ewes.

It is concluded that the pituitary glands of ovariectomized ewes with moderate levels of intake are more responsive to GnRH than those of ewes with a high intake and that hypothalamic activity and GnRH secretion are not affected by the level of food intake.

Journal of Endocrinology (1989) 121, 325–330
Pulsatile growth hormone, insulin-like growth factors and antler development in red deer (Cervus elaphus scoticus) stags
Authors: Suttie J. M. , Fennessy P. F. , Corson I. D. , Laas F. J. , Crosbie S. F. , Butler J. H. , Gluckman P. D.
Published: December 2008

Plasma samples taken every 30 min over a 26-h period each month from six 4- to 15-month-old red deer stags were analysed for GH. In addition, two samples taken at 10.00 and 22.00 h were analysed for insulin-like growth factor-I (IGF-I) and insulin-like growth factor-II (IGF-II). A concentrate diet was available ad libitum. Food intake, body weight and antler status were recorded. Concentrations of GH were analysed using the PULSAR peak detection routine. Secretion of GH was pulsatile in every month of sampling, but the pattern of pulsatility differed seasonally. During the autumn and early winter (April–June in the Southern hemisphere) GH pulses were frequent and of low amplitude. In contrast, GH pulses in spring (August–September) were of high amplitude and high frequency resulting in a high mean level of GH circulating in the plasma.

In early summer (November) the GH pulse amplitude was much lower and pulse frequency fell. There was a rise in GH pulse frequency not accompanied by an increase in GH pulse amplitude in summer (December–January). GH pulse amplitude seemed to be the main determinant of mean GH plasma level. Secretion of IGF-I was raised 1 month after peak monthly mean GH secretion. There was little consistent relationship between concentrations of IGF-II and mean daily GH. Concentrations of GH correlated positively and significantly with liveweight gain and antler growth rate with a delay of 1 month. Significantly positive correlations between concentrations of IGF-I, liveweight gain and antler growth rate were observed. It is considered that the spring and summer (September–December) seasonal acceleration of liveweight gain and antler development in stags could be a consequence of high winter/early spring (August–September) GH pulse frequency and amplitude resulting in increased concentrations of IGF-I, particularly in October.

Journal of Endocrinology (1989) 121, 351–360
Effects of amiodarone on 5′-deiodination of thyroxine to tri-iodothyronine in rat myocardium
Authors: Ceppi J. A. , Zaninovich A. A.
Published: December 2008

The present work studied the effects of amiodarone (AMD) and iopanoic acid (IA) on the conversion of thyroxine (T4) to tri-iodothyronine (T3) by rat myocardium. In vivo: male Wistar rats weighing 200–250 g were injected i.p. with AMD (2·5 mg/100 g body weight per day for 12 days) or IA (5 mg/100 g body weight every 12 h for 72 h). Hearts were then removed and processed as in the in-vitro studies. In vitro: hearts were homogenized in Krebs–Ringer phosphate buffer (pH 7·4) and AMD (0·1 mmol/l) or IA (10 mmol/l) plus dithiothreitol (8 mmol/l) and 0·01 μCi [125I]T4 or [125I]T3 were added. After incubation for 2 h at 37 °C, radioactive compounds were identified by paper chromatography. Both AMD and IA given in vivo blocked T4 to T3 conversion significantly (P<0·005). When added in vitro, AMD failed to inhibit T4 deiodination to T3 whereas IA induced a significant (P<0·005) decrease in T3 generation. Deiodination of [125I]T3 by heart homogenates was not altered by AMD or IA. While the expected increase in circulating T4 (P< 0·001) and decrease in T3 (P< 0·001) did occur after AMD or IA treatment, plasma TSH in AMD-treated rats was decreased (P<0·001), while in IA-treated animals it was increased (P< 0·001), thus indicating that AMD did not inhibit pituitary type-II 5′-monodeiodinase.

In summary, these data suggest that the hypometabolism induced by AMD in rat myocardium through a decrease in the supply of T3 is not responsible for the anti-arrhythmic activity of this drug since IA, which is not an anti-arrhythmic compound, elicited the same effect on cardiac T3. It follows that inhibition of 5′-deiodinase and the anti-arrhythmic activity of AMD are independent properties.

Journal of Endocrinology (1989) 121, 431–434