bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo and in vitro effects of dexamethasone on pituitary thyrotrophin-releasing hormone-like peptide concentrations in the rat
Authors: Akinsanya K O , Jamal H , Ghatei M A , Bloom S R
Published: December 2008

The novel peptide, pyroglutamyl-glutamyl-proline amide (pGlu-Glu-ProNH2; EEP), which has structural and immunological similarities to TRH (pGlu-His-ProNH2) has recently been shown to contribute to total TRH-like immunoreactivity (t-TRH-LI) detected in the rabbit prostate and rat and porcine anterior pituitary. In this study, the effects of dexamethasone (DEX) on rat pituitary TRH-like peptide levels in the rat were determined. TRH-like immunoreactivity (TRH-LI) was separated by ion exchange chromatography and detected by TRH RIA. Anion exchange chromatographic analysis suggested that EEP-like immunoreactivity (EEP-LI) accounted for 15·0 ± 1·2 pmol t-TRH-LI/g (70·4 ± 3·9%) in the control anterior pituitary with the remaining t-TRH-LI being due to TRH-LI.

Following DEX treatment pituitary EEP-LI and TRH-LI increased by 200% and 400% (P<0·001) respectively, constituting a 2·5-fold increase in t-TRH-LI in the pituitary. TRH-LI now accounted for 45·7±5·3% of t-TRH-LI compared with 29·6 ±4·1% in the controls. TRH-LI, but not EEP-LI, was detected in the hypothalamus and posterior pituitary, suggesting that EEP-LI is synthesised within the anterior pituitary. DEX also caused a 2·6-fold rise (P<0·001) in t-TRH-LI in dispersed, cultured anterior pituitary cells. Chromatographic analysis of cultured pituitary cell extracts revealed that the majority of t-TRH-LI (>98%) was due to TRH-LI. A possible explanation for the change in EEP-LI and TRH-LI levels in the in vivo and in vitro pituitary samples is that hypothalamic influences are necessary for the continued production of EEP-LI and are not present in vitro. Alternatively, the dissociation of the cell–cell interactions and/or the accumulation of cell products, particularly pituitary hormones in vitro, may result in a loss of the in vivo paracrine influences or the introduction of factors which inhibit EEP-LI and stimulate TRH-LI.

Journal of Endocrinology (1995) 145, 333–341
Characterization of growth hormone gene expression in the pituitary and plasma growth hormone concentrations during posthatch development in the chicken
Authors: Reiprich K , Mühlbauer E , Decuypere E , Grossmann R
Published: December 2008

In this study both sexes of two strains of chicken with genetically different growth potentials (broiler- and laying-type) were used to investigate growth hormone (GH) gene expression during posthatch development from day 7 (D7) to D56 by using the in situ hybridization technique and Northern analysis. In pituitaries of both strains a high GH mRNA signal was found as early as D7 by in situ hybridization, showing clear differences in the pattern of gene expression between the two strains. By Northern hybridization sex differences were detectable in all age groups of broilers, with higher levels throughout in males. In layers, however, females showed consistently higher levels compared with males until D21. While signal intensities decreased in the broiler strain during the investigation period, the layer-type strain seemed to express GH mRNA more continuously, reaching significantly (P<0·01) higher GH mRNA levels than broilers at D56. Plasma GH concentrations ran parallel to GH mRNA in early stages but showed a peak earlier at D14 and decreased after D35 in both sexes and strains. Determination of growth as weekly weight gains, however, proved that a period of rapid growth (at a higher level in both sexes of the broiler strain) at D7 was followed by a strong decrease from D14 to D21. A plateau of constant growth was reached until the end of the observation period with similar rates in both strains and sexes. Analysis of plasma thyroid hormones tri-iodothyronine/thyroxine (T3/T4) showed an increase in T3 concentrations in both strains and sexes in early stages and a decrease thereafter. No clear strain differences were measured. T4 plasma concentrations increased from D7 to D14 in broilers and D21 in layers when a plateau was reached. From the results we conclude that generally there is a good correlation between GH mRNA and plasma GH concentrations in both strains investigated. Neither parameter, however, is coupled directly with the growth rate. Thus the early rapid growth corresponds to relatively low levels of GH mRNA and plasma GH concentrations, but high T3 levels. Later, decreased growth rates are linked to increasing amounts of GH mRNA as well as increasing plasma GH concentrations in both layers and broilers. Towards the end of the observation period there was a strain divergence visible with increased amounts of GH mRNA in layers but a strong reduction in broilers. Moreover, plasma GH concentrations decreased more slowly in layers than in broilers.

Journal of Endocrinology (1995) 145, 343–353
ACTH-induced c-myc proto-oncogene expression precedes antimitogenic effect during differentiation of fetal rat adrenocortical cells
Authors: Heikkilä P , Arola J , Salmi A , Kahri A I
Published: December 2008

The regulation of proto-oncogenes has been connected with proliferation and differentiation in various cell types. In the present study, the ACTH-induced expression of c-myc mRNA and proliferation of fetal rat adrenocortical cells have been studied. Low levels of c-myc mRNA were detected in undifferentiated zona glomerulosa-like cells. Stimulation with ACTH for 2 to 6 h transiently increased the c-myc mRNA levels. Both basal and ACTH-induced expression levels were increased by the protein synthesis inhibitor cycloheximide. Treatment with a protein kinase C (PKC) activator 12–0-tetradecanoyl phorbol-13-acetate mimicked the effect of ACTH, whereas c-myc mRNA levels decreased by inhibiting the PKC with H-7. ACTH inhibited proliferation of fetal rat adrenocortical cells during the first 24 h of stimulation. The inhibitory effect began from 6 h, reached its maximum at 12 h and slowly vanished at 24 h.

Our data demonstrated that ACTH transiently increased c-myc mRNA expression. Adrenocortical c-myc expression was mediated via PKC. In contrast to previous reports, where c-myc expression precedes proliferation of various cells, ACTH-induced c-myc mRNA expression of cultured fetal rat adrenocortical cells was followed by inhibition of proliferation.

Journal of Endocrinology (1995) 145, 379–385
Luminal glucagon-like peptide-1(7–36) amide-releasing factors in the isolated vascularly perfused rat colon
Authors: Plaisancié P , Dumoulin V , Chayvialle J-A , Cuber J-C
Published: December 2008

Glucagon-like peptide-1 (GLP-1) is released from endocrine cells of the distal part of the gut after ingestion of a meal. GLP-1 secretion is, in part, under the control of hormonal and/or neural mechanisms. However, stimulation of the colonic L cells may also occur directly by the luminal contents. This was examined in the present study, using an isolated vascularly perfused rat colon. GLP-1 immunoreactivity was measured in the portal effluent after luminal infusion of a variety of compounds which are found in colonic contents (nutrients, fibers, bile acids, short-chain fatty acids (SCFAs)). Oleic acid (100 mm) or a mixture of amino acids (total concentration 250 mm), or starch (0·5%, w/v) did not increase GLP-1 secretion over basal value. A pharmacological concentration of glucose (250 mm) elicited a marked release of GLP-1 which was maximal at the end of infusion (400% of basal), while 5 mm glucose was without effect on secretion. Pectin evoked a dose-dependent release of GLP-1 over the range 0·1–0·5% (w/v) with a maximal response at 360% of basal when 0·5% pectin was infused. Cellulose or gum arabic (0·5%) did not modify GLP-1 secretion. The SCFAs acetate, propionate or butyrate (5, 20 and 100 mm) did not induce a significant release of GLP-1. Among the four bile acids tested, namely taurocholate, cholate, deoxycholate and hyodeoxycholate, the last one was the most potent at eliciting a GLP-1 response with a maximal release at 300% and 400% of the basal value when 2 and 20 mm bile acid were administered respectively. In conclusion, some fibres and bile acids are capable of releasing colonic GLP-1 in rats and may contribute to the secretory activity of colonic L cells.

Journal of Endocrinology (1995) 145, 521–526
Differences in carbohydrate composition of FSH preparations detected with lectin-ELISA systems
Authors: Rafferty B , Mower J A , Ward H L , Rose M
Published: December 2008

FSH is a glycoprotein containing N-linked carbohydrates which exhibit a variety of forms ranging from mono- to multibranched structures. Variation in glycosylation, particularly the degree of terminal sialylation, determines the half-life of the hormone and hence its in vivo bioactivity. The glycoform content of FSH preparations can differ according to the source (e.g. pituitary, urine), cell line (for rDNA-derived material) and selectivity of purification procedures, and may create difficulties in the preparation and characterization of standards and therapeutic products. In order to develop a simple method to detect changes in glycocomposition, an FSH ELISA was modified by the incorporation of lectins of recognized sugar specificity, and used to examine the terminal sugar composition of ampouled preparations of pituitary, urinary and rDNA-derived FSH.

FSH was captured with a specific monoclonal antibody (MAb) and detected with either biotinylated anti-FSH MAb (ELISA) or the sugar-specific lectins (L-ELISA) from Triticum vulgaris (sialic acid, SA), Sambucus nigra (α2,6-linked SA), Maackia amurensis (α2,3-linked SA) or Ricinus communis (free terminal galactose; GAL). Relative estimates of the amounts of terminal SA, its different forms and GAL were derived from the L-ELISA/ELISA data compared with the highly sialylated 1st International Standard for pituitary FSH (IS) 83/575.

All the FSH preparations had less SA than the IS with the ratio of α2,3- and α2,6-linked SA varying between preparations. The amounts of α2,6-linked SA relative to the IS were not significantly different in the urinary and pituitary preparations whereas α2,3-linked SA in all preparations was generally less than that of the standard. The rDNA FSH material, produced in CHO cells, was confirmed as containing only α2,3-linked SA. The degree of asialylation revealed by the Ricinus lectin showed that the more heavily sialylated IS had less exposed GAL than the other preparations. The method provides a simple and rapid technique for assessing changes in terminal sugar composition and allows comparison of the patterns of terminal glycosylation between preparations from different sources and, when assayed against the appropriate standard, between batches of therapeutic products.

Journal of Endocrinology (1995) 145, 527–533
Developmental regulation of androgen receptor in rat ovary
Authors: Tetsuka M , Whitelaw P F , Bremner W J , Millar M R , Smyth C D , Hillier S G
Published: December 2008

Androgen receptor (AR) distribution and developmental regulation in the rat ovary were examined by semiquantitative immunohistochemistry. Ovarian AR mRNA levels were also determined by Northern analysis of total RNA and compared with the levels of cytochrome P450aromatase (P450arom), an established marker of preovulatory follicular maturity. Hypophysectomized immature female rats were treated with recombinant human (rh)-FSH and/or rh-LH, or human menopausal gonadotrophin (HMG). AR was predominately located in granulosa cells. There was no indication of specific AR immunoreactivity in thecal cells, but scattered stromal cells did stain positively. In control and LH-treated ovaries, only small preantral/early antral follicles were present. Granulosa cells in these follicles showed intense AR immunostaining. Treatment with FSH, FSH and LH or HMG stimulated varying degrees of preovulatory follicular development. In these follicles, the intensity of AR immunostaining progressively declined as follicular development progressed. In intact immature rats treated with FSH, the abundance of ovarian AR mRNA was significantly decreased to 35% of the control value while combined treatment of FSH and LH resulted in further down-regulation of AR mRNA expression to 17% of the control value. A decrease in the abundance of AR mRNA was accompanied by a simultaneous increase in the abundance of P450arom mRNA. Similar results were obtained in hypophysectomized immature rats treated with FSH and LH, suggesting an inverse relationship between AR mRNA expression and granulosa cell maturity. These results suggest that (1) the AR is most abundant in the granulosa cells of rat ovaries and (2) the expression of AR and its mRNA are developmentally regulated, being down-regulated during FSH-stimulated preovulatory follicular development.

Journal of Endocrinology (1995) 145, 535–543
Circulating insulin-like growth factors (IGFs), IGF-binding proteins (IGFBPs) and tissue mRNA levels of IGFBP-2 and IGFBP-4 in the ovine fetus
Authors: Carr J M , Owens J A , Grant P A , Walton P E , Owens P C , Wallace J C
Published: December 2008

The IGF-binding proteins (IGFBPs) are a family of at least six structurally related proteins, which bind the IGFs and modulate their actions, including the regulation of preand postnatal growth. In this study we have examined the relationship between circulating and tissue mRNA levels of IGFBPs and related this to circulating IGFs in the fetal sheep over the gestational period when rapid growth and development occurs. Circulating IGFBP-2, as measured by Western ligand blot (WLB), increases between early and mid gestation, remains high, then declines throughout late gestation (P=0·0002). Circulating IGFBP-3 increases throughout gestation, as measured by WLB or RIA (P=0·04 and P=0·0001 respectively), as does circulating IGFBP-4 (P=0·004). These ontogenic changes in circulating IGFBPs-2 and -4 are paralleled by changes in liver mRNA for these proteins and, for IGFBP-2, by those in kidney IGFBP-2 mRNA also. This suggests that liver and kidney may be the primary contributors to circulating IGFBP-2 and the liver to circulating IGFBP-4. IGFBP-2 mRNA is present in the heart and lung in early gestation but barely detectable in these tissues after approximately 60 days gestation. IGFBP-4 mRNA is also present in the heart in early but not late gestation, but is abundant in the lung throughout gestation. These results demonstrate tissue specific and developmental regulation of IGFBPs-2 and -4 at the mRNA level. To assess any role the circulating IGFs may play in mediating these changes in IGFBPs, or vice versa, both plasma IGF-I and IGF-II were measured by RIA. Circulating IGF-I increases as gestation progresses (P=0·0001), while circulating IGF-II increases between early and mid gestation, remains high (P=0·01), then declines. Circulating IGF-I is positively correlated with fetal weight (r=0·66, P=0·03), circulating IGFBP-3 (r=0·54, P=0·01) and IGFBP-4 (r=0·52, P=0·01). Circulating IGF-II positively correlates with circulating IGFBP-2 (r=0·48, P=0·02) throughout gestation and at 1 day postnatally. These relationships are consistent with circulating IGF-I influencing IGFBPs-3 and -4, and similarly, IGF-II determining IGFBP-2, or vice versa. Alternatively, these correlations may reflect coordinate regulation of IGF and IGFBP by a common factor.

Journal of Endocrinology (1995) 145, 545–557
Effects of ovarian steroids on hypothalamic opioid receptor subtypes in ovariectomized ewes: regional changes in density and affinity
Authors: Shen P J , Smith A I , Evans R G , Clarke I J
Published: December 2008

The negative feedback regulation by ovarian steroids of luteinizing hormone secretion may be partially mediated by a hypothalamic endogenous opioid mechanism. This could be affected by ovarian steroid-regulated changes in hypothalamic opioid receptor binding mechanisms. In this report we show that in the presence of blocking concentrations of site-selective opioid analogues, [3H]diprenorphin homogeneously labelled μ, δ or κ receptor subtypes respectively. Using this receptor binding model, we characterized each opioid receptor subtype in the hypothalamic preoptic area and medio-basal hypothalamus of ovariectomized (OVX) and OVX plus progesterone- or oestradiol-17β (OE2)-treated ewes. In the preoptic area, progesterone treatment did not influence the affinity or capacity of δ or κ receptor binding sites, but significantly reduced μ receptor subtype content (20% less than control) with no statistically significant change in affinity. There was no effect of OE2 on either the affinity or capacity of each opioid receptor subtype in this area. In the mediobasal hypothalamus, progesterone treatment significantly decreased δ subtype receptor affinity (22 ± 11 nm vs control 7 ± 2 nm) and increased binding capacity (78 ± 9 fmol/mg protein vs control 37 ± 16 fmol/mg protein). OE2 treatment had a similar, though more profound effect on affinity (51 ± 17 nm) and binding capacity (139 ± 26 fmol/mg protein) at the δ receptor binding site. There were no significant changes in the affinity or capacity of μ or κ binding sites in the medio-basal hypothalamus. These results indicate that steroid hormones modulate hypothalamic opioid receptors in the OVX ewe in a receptor subtype- and region-dependent manner. The precise role of these steroid-induced changes in opioid receptor characteristics remains to be determined.

Journal of Endocrinology (1995) 145, 559–567
Relative roles of the thyroid hormones and noradrenaline on the thermogenic activity of brown adipose tissue in the rat
Authors: Cageao L F , Noli M I , Mignone I R , Farber M , Ricci C R , Hagmüller K , Zaninovich A A
Published: December 2008

We have assessed the relative contribution of the thyroid hormones and noradrenaline (NA) on the calorigenic function of brown adipose tissue (BAT) as indicated by GDP binding and O2 consumption of BAT mitochondria. Male Wistar rats of 200 g body weight were made hypothyroid with 131I. Groups of animals were injected s.c., in divided doses, daily for 10 days, with thyroxine (2 μg/100 g body weight) or tri-iodothyronine (T3; 0·3 μg/100 g body weight). Animals were used 7 days after bilateral or unilateral sympathetic nerve excision of BAT (Sx). Sham-operated rats were used as controls. In normal rats kept at 22 °C, GDP binding reached 94 ± 24 pmol/mg protein; untreated hypothyroid rats had normal binding values whereas the T3-treated group showed an increased binding. Sx induced a sharp fall in the three groups (P<0·01). After 24-h exposure to 4 °C GDP binding increased in normal rats to about 410% (P<0·01) whereas binding failed to increase in response to cold in the untreated hypothyroid and the T3-treated groups. Sx reduced GDP binding in the three groups significantly (P<0·01). The consumption of O2 by BAT mitochondria showed similar variations in response to Sx and to cold exposure as did GDP binding. The data indicated that, at room temperature, BAT calorigenesis can function without the thyroid hormones, though not without the catecholamines. The findings in rats exposed to cold showed that the lack of NA was significantly more effective than the lack of thyroid hormones in preventing the BAT hyperactive response. This does not negate an active role for T3 in BAT calorigenesis.

Journal of Endocrinology (1995) 145, 579–584
Testicular serotonin is related to mast cells but not to Leydig cells in the rat
Authors: Aguilar R , Antón F , Bellido C , Aguilar E , Gaytan F
Published: December 2008

Testicular serotonin (5HT) concentrations were determined by HPLC in the testes of rats treated neonatally with oestradiol benzoate (EB) and in adult rats treated with the Leydig cell cytotoxic ethylene dimethane sulphonate (EDS). 5HT concentrations were related to mast cell numbers. EB-treated rats showed an accumulation of mast cells in the testes at 35 and 70 days of age and increased 5HT concentrations in both the interstitial fluid and the testicular capsule, whereas no increases in 5HT concentrations or in the number of mast cells were found for the ventral prostate of these animals. On the contrary, 5HT concentrations were not related to the number of Leydig cells. In EB-treated rats, in which Leydig cells were nearly absent at 35 days of age, 5HT concentrations were significantly increased. Furthermore, EDS-treated rats did not show significant changes in 5HT concentrations, in spite of the elimination of Leydig cells. These data suggest that mast cells are a major source of serotonin in the rat testis.

Journal of Endocrinology (1995) 146, 15–21
Retinoids: transport, metabolism, and mechanisms of action
Authors: Vieira A V , Schneider W J , Vieira P M
Published: December 2008

The retinoids comprise a family of polyisoprenoid lipids that includes vitamin A (retinol) and structurally related compounds. The biological activity of retinoids can be modified, for example, by changes in the molecules' state of oxidation and cis/trans isomerization. Their activity is also dependent on the levels of specific types of retinoid-binding proteins which exist in extracellular, cytosolic and nuclear compartments. The role of retinoids in gene expression represents an important biological function for this family of molecules. Retinoid-dependent modulation of gene expression is critical for normal cell and tissue function in mature as well as developing animals. Despite significant advances in the understanding of retinoid biological activity, important questions remain concerning aspects of retinoid metabohsm, cellular uptake, intracellular trafficking and regulation of gene transcription. The purpose of this review is to present these topics as a compendium of retinoid endocrinology.
Effects of sodium depletion on the response of rat adrenal zona glomerulosa cells to stimulation by neuropeptides: actions of vasoactive intestinal peptide, enkephalin, substance P, neuropeptide Y and corticotrophin-releasing hormone
Authors: Hinson J P , Kapas S
Published: December 2008

There are several neuropeptides, present in nerves supplying the rat adrenal zona glomerulosa, which have been shown to stimulate aldosterone secretion in the intact perfused rat adrenal preparation. The purpose of the present study was twofold: first, to determine whether these peptides acted directly on adrenocortical cells by examining their effects on collagenase-dispersed rat zona glomerulosa cells, and second, to investigate the likely physiological significance of these actions, by determining whether the responses of zona glomerulosa cells to neuropeptides were changed by prior sodium depletion.

Of the peptides tested, neuropeptide Y (NPY) and substance P had only a minor effect on aldosterone secretion, which was not substantially affected by sodium depletion. Corticotrophin-releasing hormone (CRH) had a significant stimulatory effect on aldosterone secretion, but neither the threshold concentration for significant stimulation nor the maximal response to stimulation were altered by prior sodium depletion.

Vasoactive intestinal peptide (VIP), on the other hand, had little effect on aldosterone secretion by cells from normal animals, but was a potent stimulus to aldosterone secretion in cells obtained from sodium-depleted animals. The response to the Met-enkephalin analogue, [d-Ala2-Met2]-enkephalinamide (DALA), was also significantly enhanced by prior sodium depletion. Experiments using the angiotensin II receptor blocker, saralasin, were carried out to determine whether the enhanced actions of DALA and VIP seen in sodium depletion may be a result of activation of angiotensin II receptors, known to be increased in sodium depletion. Saralasin did not affect the response to either peptide.

These data suggest that all the peptides tested may be able to stimulate aldosterone secretion. However, the data obtained with substance P, NPY and CRH do not support a major role for these peptides in the regulation of aldosterone secretion either under control conditions, or in sodium depletion. The finding that the responses to VIP and DALA were altered by sodium depletion suggests that the actions of VIP and opioid peptides may have physiological significance in the regulation of aldosterone secretion in response to sodium depletion. Furthermore, the observation that saralasin does not inhibit the responses to these peptides strongly suggests that they are not acting through angiotensin II receptors, and may indicate altered VIP- and opioid-receptor regulation in sodium depletion.

Journal of Endocrinology (1995) 146, 209–214
Hormonal control of insulin-like growth factor-I and growth hormone receptor mRNA expression by porcine hepatocytes in culture
Authors: Brameld J M , Weller P A , Saunders J C , Buttery P J , Gilmour R S
Published: December 2008

The effects of various hormones commonly added to hepatocyte culture media upon the expression of the GH receptor (GHR) and insulin-like growth factor-I (IGF-I) genes in cultured porcine hepatocytes were investigated. Preliminary investigations indicated that there was an absolute requirement only for insulin, with high losses of cell viability upon long term exclusion of insulin from the culture medium. The decline in GHR expression with time in culture was found to be less when high levels of glucose were included in the medium. Therefore the basal culture medium used in these studies was Williams' medium E supplemented with 0·2% (w/v) BSA, 5000 mg glucose/l and 100 nmol porcine insulin/l. The addition of dexamethasone (100 nmol/l) increased the expression of both GHR and IGF-I (class 1 transcripts only) mRNA (P<0·001 and P<0·05 respectively), and resulted in an increased responsiveness of IGF-I mRNA expression to GH (1 μg/ml), when the two were added in combination (although only class 1 transcripts were shown to be statistically significant, P<0·01). The addition of either thyroid hormone (1 nmol/l T3 or T4) alone also increased the expression of GHR mRNA (P<0·01) in addition to the dexamethasone stimulated expression, with T4 appearing to decrease IGF-I expression slightly (P<0·05) (either on its own or with T3). As with dexamethasone, the thyroid hormones increased the response of IGF-I mRNA expression to GH (1 μg/ml) when added in combination with GH (P<0·001). These observations demonstrate one possible mechanism for the interactions of glucocorticoids and thyroid hormones with the GH–IGF axis.

Journal of Endocrinology (1995) 146, 239–245
Long R3 insulin-like growth factor-I (IGF-I) infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig
Authors: Conlon M A , Tomas F M , Owens P C , Wallace J C , Howarth G S , Ballard F J
Published: December 2008

We have tested whether an animal with substantial amounts of both IGF-I and IGF-II in circulation, such as the guinea pig, would respond to chronic IGF infusion in the same manner as the adult rat, which has negligible amounts of IGF-II in blood. Female guinea pigs of 350 g body weight were continuously infused for 7 days with recombinant guinea pig IGF-I or -II (120 or 360 μg/day) or long R3 IGF-I (LR3IGF-I) (120 μg/day), an analogue which has much reduced affinities for IGF binding proteins. IGF-I or IGF-II infusion led to substantial increases in plasma IGF-I or IGF-II respectively in comparison with vehicle-infused animals. Nevertheless, body weight gain, feed intake, feed conversion efficiency and carcass composition were not significantly affected by any treatment (significance was deemed to be P<0·05). Amongst the tissues examined only the fractional weight (g/kg body weight) of the adrenals was increased, and that only by the higher dose (360 μg/day) of IGF-I. However, the fractional weight of adrenals, gut, kidneys and spleen were significantly increased by LR3IGF-I, but again overall growth was not stimulated. A possible explanation for the lack of IGF-I effects is that total circulating IGF concentrations were not increased by these treatments. IGF-II significantly raised total IGF concentrations at the higher dose only. Plasma IGF-I was reduced by IGF-II infusion, as was plasma IGF-II by IGF-I infusion. LR3IGF-I treatment lowered both plasma IGF-I and IGF-II concentrations, a response probably related to a reduction in total plasma IGF binding protein (IGFBP), especially IGFBP-3, concentrations. We conclude that although the guinea pig is responsive to IGF treatment, the effects differ markedly from those elicited in rats.

Journal of Endocrinology (1995) 146, 247–253
Inverse control of growth hormone and prolactin secretion in clonidine-stimulated dairy cattle
Authors: Borromeo V , Berrini A , Möller F , Secchi C
Published: December 2008

Clonidine is a specific α-2-adrenoreceptor agonist that stimulates growth hormone (GH) release in animals and humans. This drug was used to study the GH and prolactin (PRL) secretory response in dairy cows and heifers. An i.v. infusion of 10 μg/kg body weight induced GH release to a peak concentration after 30–60 min, while 2 μg/kg had no effect on GH secretory patterns. Plasma PRL decreased significantly (P<0·01) starting 15–60 min after both doses of clonidine, this effect lasting up to 6 h. Clonidine significantly lowered plasma insulin (P<0·01) and raised plasma glucose (P<0·01). The changes in plasma GH, PRL, insulin and glucose differed significantly between doses, the 10 μg/kg dose being more effective (P<0·01). The results of our investigation in dairy cattle provide evidence of (i) an increase in GH release after 10 μg/kg clonidine; (ii) a concomitant decrease in PRL secretion, hence GH and PRL secretion in cattle appear inversely controlled; (iii) a significant difference between the effects of the 2 and 10 μg/kg doses and (iv) no relationship between the changes in plasma GH and PRL after clonidine and plasma hormone levels before treatment.

Journal of Endocrinology (1995) 146, 271–277
The effects of oestradiol and relaxin on extensibility and collagen organisation of the pregnant rat cervix
Authors: Cheah S H , Ng K H , Johgalingam V T , Ragavan M
Published: December 2008

The effects of exogenously introduced oestradiol-17β (E) and relaxin (RLX) on cervical extensibility and collagen organisation were tested in rats ovariectomised in late pregnancy. When the cervices were stretched in vitro by 1 mm increments, it was found that those from rats given E alone generated significantly higher tensions than those from control rats, while cervices from rats given both E and RLX had tensions similar to controls. Examination of cervical sections under the light microscope and ultra-thin sections under the electron microscope showed that the collagen fibres in the cervices from E-treated rats were highly organised, whereas those from animals given E+RLX and control animals were disorganised and dispersed. It was concluded that E decreased cervical extensibility, while RLX counteracted the effect of E to maintain a soft and easily extensible cervix.

Journal of Endocrinology (1995) 146, 331–337
Basal tail skin temperature elevation and augmented response to calcitonin gene-related peptide in ovariectomized rats
Authors: Kobayashi T , Ushijima O , Chen J-T , Shiraki M , Ohta T , Kiyoki M
Published: December 2008

Hyper-release of calcitonin gene-related peptide (CGRP) plays a direct and pivotal role in the induction of menopausal hot flushes (HFs), in which a drastic increase in skin temperature occurs. However, it is not possible to investigate whether CGRP induces skin temperature increase and whether skin temperature response to CGRP changes and contributes to the occurrence of HFs in postmenopausal women who are in oestrogen deficiency. By using rats' tail skin temperature (TST), a good marker to evaluate skin temperature regulation, we examined the effects of CGRP and calcitonin (3, 10 and 30 μg/kg, i.v.) on TST in female rats and further investigated the TST change induced by CGRP (10 μg/kg, i.v.) in ovariectomized (OVX) rats compared with that in sham-operated (Sham) rats. We found that CGRP, but not calcitonin, induced a TST increase in a dose-dependent manner and that the TST change induced by CGRP (0·6 ±0·2 °C for OVX rats vs 0·3 ±0·1 °C for Sham rats, P<0·05) and also the basal TST (26·0 ± 0·2 °C for OVX rats vs 25·5 ±0·1 °C for Sham rats) were significantly greater in OVX rats (P<0·05). Furthermore, treatment with oestradiol (30 μg/kg, s.c.) for 8 days partially inhibited the augmented TST response to CGRP in OVX rats and almost completely inhibited (P<0·05) the basal TST elevation, with the concomitant recovery of the serum oestradiol level to that in Sham rats. These results suggest that the augmented skin temperature response to CGRP and the elevation of basal skin temperature that are found in OVX rats, animals which are oestradiol deficient, may also occur in menopausal women and contribute to their HFs.

Journal of Endocrinology (1995) 146, 431–437
Thyroid glands: novel sites of growth hormone action
Authors: Hull K L , Janssens W C J , Baumbach W R , Harvey S
Published: December 2008

Thyroid hormones inhibit the synthesis and release of GH in avian species. This may represent a feedback mechanism, since GH enhances the peripheral production of tri-iodothyronine (T3). The possibility that GH may also have direct effects on thyroidal function was therefore investigated.

The basal and thyrotrophin-induced release of thyroxine (T4) from incubated chicken thyroid glands was not enhanced, however, in the presence of chicken GH. Contrarily, GH impaired T4 release in a dose-related way. These actions were probably mediated by specific receptors, since binding sites for radiolabelled GH were demonstrated on the plasma membranes of chicken thyroid glands. Expression of the GH receptor gene in these tissues was also demonstrated using a cRNA probe for the rabbit liver GH receptor, which specifically hybridized with RNA moieties of 4·4 kb, 2·7 kb and 1·0 kb. Moreover, reverse transcription of thyroidal RNA and its amplification in the presence of 3′- and 5′-oligonucleotide primers coding for the extracellular or intracellular domains of the GH receptor generated electrophoretically separable fragments of 500 bp and 800 bp respectively, as would be expected from analysis of the hepatic GH receptor cDNA sequence. Digestion of the 500 bp fragment with NcoI or EcoRI also produced moieties of expected size (350 bp and 150 bp or 325 bp and 175 bp respectively), as did BamHI or HaeIII digestion of the 800 bp fragment (yielding fragments of 550 bp and 275 bp or 469 bp and 337 bp respectively). Translation of the GH receptor mRNA was also indicated by the immunocytochemical demonstration of GH receptors in thyroid follicular and parafollicular cells, using a specific polyclonal antibody raised against the chicken GH-binding protein.

These results therefore provide evidence, for the first time, of GH receptor gene expression in thyroid tissue and the translation of functional GH receptors in thyroid glands. These results also demonstrate differential effects of GH on the extracellular concentrations of T3 and T4, which may permit subtle regulation within the somatotroph-thyroid axis.

Journal of Endocrinology (1995) 146, 449–458
Mechanisms of altered LH secretion in neonatally oestrogenized male rats
Authors: Pinilla L , Tena-Sempere M , Gonzalez D , Aguilar E
Published: December 2008

It is well known that the control of LH secretion depends on the steroid milieu during the postnatal period. In this study LH secretion was analysed in adult male rats injected neonatally with 500 μg oestradiol benzoate (1) after orchidectomy, (2) after selective elimination of androgens by destruction of Leydig cells with ethylene dimethane sulphonate (EDS), and (3) after removal in orchidectomized animals of Silastic capsules containing testosterone. In addition, (4) in vivo and in vitro LH secretion in response to LHRH agonist and antagonists, (5) the hypothalamic LHRH content, (6) the basal and stimulated in vitro LHRH release, and (7) the LH responses after administration of naloxone (2 mg/kg), α-methyl-p-tyrosine (α-MPT; 250 mg/kg), N-methyl-d-aspartic acid (NMDA, 15 mg/kg) or kainic acid (KA; 15 mg/kg) were also examined. Our data indicated that (1) the LH response after orchidectomy, after EDS administration and after removal of Silastic capsules containing testosterone was diminished in oestrogenized male rats, (2) the pituitaries from oestrogenized males retained responsiveness to LHRH, (3) hypothalamic LHRH content was reduced in oestrogenized males, but the hypothalamus from oestrogenized males released more LHRH than those of control groups both under basal conditions or after depolarization, (4) α-MPT decreased LH secretion only in oestrogenized males, and (5) NMDA and KA stimulated LH only in oestrogenized males. We conclude that in oestrogenized male rats the loss of sensitivity to the negative feedback action of testosterone on LH secretion was not due to decreased pituitary responsiveness to LHRH stimulation or to the inherent damage of LHRH neurones. In contrast, changes in the mechanisms governing LHRH release seem to be involved. A lack of activation of the excitatory noradrenergic and aminoacidergic systems seems to be part of the neurochemical basis of altered gonadotrophin secretion in neonatally oestrogenized male rats.

Journal of Endocrinology (1995) 147, 43–50
A 67 kDa protein mediates pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal peptide-stimulated insulin secretion in a hamster clonal β-cell line
Authors: Kulkarni R N , Smith D M , Ghatei M A , Bloom S R
Published: December 2008

Insulin secretion is regulated by neural and neurohormonal factors. The report of nerves releasing pituitary adenylate cyclase-activating polypeptide (PACAP) – a 38 amino acid peptide – in the endocrine pancreas, suggests it may be important in modulating insulin release. We therefore carried out receptor-binding studies on membranes prepared from the glucose-responsive clonal β-cell line HIT-T15, and also examined the effects of PACAP38, PACAP27 – a C-terminal truncated form of the peptide – and vasoactive intestinal peptide (VIP) on insulin and islet amyloid polypeptide (IAPP) release. We showed by chemical cross-linking that PACAP and VIP stimulate secretion from the clonal cells by binding to a receptor with a molecular weight of 67 kDa (n=4). Binding was saturable when membranes were incubated with 125I-PACAP27 (Kd 1·2±0·2 nm; Bmax 415·7±35·3 fmol/mg; n=4) or 125I-VIP (Kd 1·3±0·3 nm; Bmax 354·8 ± 42·8 fmol/mg; n=4). We also demonstrated an increase in glucose-stimulated insulin (PACAP27, 366·6 ±25·8% PACAP38, 389·9 ±13·4%; VIP, 342·6± 16·1% of control; all at 1 μm, P<0·01 vs control) and IAPP release (PACAP27, 236·9 ±26·2%; PACAP38, 226·5 ± 10·9%; VIP, 242·9 ± 15·8% of control; all at 1 μm, P<0·01 vs control). Incubation of the cells with these peptides, for a duration of 12 h, in the presence of 5·5 mm glucose, did not alter the expression of insulin or IAPP. These findings suggest that PACAP and VIP stimulate secretion of insulin and IAPP by binding to a 67 kDa protein on clonal β-cells and do not alter the transcription of insulin and IAPP under the conditions tested.

Journal of Endocrinology (1995) 147, 121–130
Tumour necrosis factor a, interferon γ and dexamethasone regulate IGF-I-maintained collagen production in cultured human fibroblasts
Authors: Bird J L E , Tyler J A
Published: December 2008

We examined the effects of tumour necrosis factor α (TNFα) and interferon γ (IFNγ) on the production of collagen by human infant foreskin fibroblasts. Collagen synthesis was maintained in the presence of IGF-I so that cytokine effects could be examined in the absence of serum. TNFα inhibited IGF-I-maintained collagen production in a dose-dependent manner. Maximal suppression of 50% was attained at a concentration of 7·5 ng/ml. IFNγ also suppressed collagen accumulation in IGF-I-maintained cells, with a maximal inhibition to 55% at 375 U/ml. The rate of collagen formation relative to total protein production for secreted proteins was calculated. This value decreased from 10·3% for IGF-I-cultured cells to 6·2% and 8·4% with the inclusion of TNFα and IFNγ respectively, indicating that inhibition was selective for collagen. TNFα (5 ng/ml) and IFNγ (250 U/ml) together suppressed IGF-I-maintained collagen production to approximately 35%, with a decrease from 10·3% to 2·9% in collagen production relative to total protein. The inclusion of a serum-free period prior to the addition of TNFα to the cultures resulted in a further inhibition to 15% of control. This increase in inhibition was not seen if dexamethasone was present in the serum-free period prior to cytokine addition. These data showed that IGF-Imaintained collagen formation is suppressed by the proinflammatory cytokines TNFα and IFNγ, and that these interactions are influenced by dexamethasone. Proinflammatory cytokines interact in a complex manner with other serum factors to modulate IGF-I-stimulated extracellular matrix production and may have important roles in regulating tissue repair.

Journal of Endocrinology (1995) 147, 167–176
Urinary clearance of atrial natriuretic peptide in Pekin ducks
Authors: Gray D A
Published: December 2008

To quantify the renal excretion of atrial natriuretic peptide (ANP) in birds, synthetic ANP was infused intravenously into conscious Pekin ducks at rates of 10, 30 and 90 ng/kg per min for 30 min and the relationships between plasma and urine ANP concentrations were monitored by RIA. The infusions of ANP produced dose-dependent elevations in the plasma concentrations of the hormone; however, urinary concentrations and excretion rates did not change significantly from the basal values of 142·2 ±21·5 pg/ml and 26·4 ± 4·5 pg/min per kg respectively. The metabolic clearance rate of ANP remained constant at each infusion dose (approximately 200 ml/min per kg). The urinary clearance rates (<0·3 ml/min per kg) indicated that the fraction of ANP cleared from the blood via the urine was less than 0·2%. Clearly, excretion of intact ANP via this route is not a quantitatively important means of elimination for this hormone in birds.

Journal of Endocrinology (1995) 147, 211–215
Changes in inhibin-A (α-βA dimer) and total α inhibin in the peripheral circulation and ovaries of rats after gonadotrophin-induced follicular development and during the normal oestrous cycle
Authors: Fahy P A , Wilson C A , Beard A J , Groome N P , Knight P G
Published: December 2008

Recent modifications to a previously reported two-site IRMA have permitted the measurement of serum/plasma concentrations and ovarian contents of inhibin-A (α-βA dimer) in pregnant mare serum gonadotrophin (PMSG)treated immature female rats and adult rats throughout the 4-day oestrous cycle. For comparison, total α inhibin levels were also measured by α subunit-directed inhibin RIA and found to be at least tenfold higher (relative to the same 32 kDa bovine inhibin standard used to calibrate both assays). In immature female rats, serum levels of inhibin-A dimer and total α inhibin increased within 3 h of PMSG injection and rose in parallel over the next 48 h to values four- to fivefold higher than pretreatment levels. Ovariectomy led to a rapid and parallel fall in both inhibin-A dimer and total α inhibin; initial half-lives (±95% confidence intervals) were 22 ± 4 and 20 ± 5 min respectively. In adult rats, marked fluctuations in plasma concentrations and ovarian contents of inhibin-A dimer and total α inhibin occurred during the 4-day oestrous cycle, most notably between the morning of pro-oestrus and the morning of oestrus. Plasma levels of inhibin-A dimer and total α inhibin peaked on the afternoon of pro-oestrus just before the preovulatory gonadotrophin surge. After ovulation, both inhibin-A dimer and total α inhibin fell abruptly (two- to threefold by 0200 h on oestrus; P<0·001), while FSH showed a secondary rise which peaked at 0700 h on oestrus. Although IRMA- and RIA-derived inhibin values generally followed a similar pattern across the 4-day cycle (plasma: r=0·52, P<0·001; ovary: r=0·41, P<0·001), a transient rise in plasma and ovarian inhibin-A dimer was detected at 0700 h on oestrus (P<0·01) which was unaccompanied by a rise in total α inhibin. This rise in plasma inhibin-A dimer was probably responsible for terminating the post-ovulatory FSH surge since FSH levels declined steadily over the next 15 h. Overall, plasma inhibin-A dimer and FSH concentrations across the whole cycle were negatively correlated (r= −0·22, P<0·01) whereas no correlation existed between total α inhibin and FSH (r= −0·11, P=0·12).

Journal of Endocrinology (1995) 147, 271–283
Multiple mechanisms of heterologous β-adrenoceptor regulation in rat uterus
Authors: Nimmo A J , Whitaker E M , Morrison J F B , Carstairs J R
Published: December 2008

The inhibitory effects of catecholamines on rat myometrium mediated by β-adrenoceptors are modulated by ovarian steroids. Previously reported findings of radioligand binding studies on myometrial membranes have demonstrated changes in the numbers of β-adrenergic binding sites following ovarian steroid treatment. However, these changes were not accompanied by parallel functional changes. In the present study, we have investigated possible mechanisms of heterologous β-adrenoceptor regulation by ovarian steroids. Binding studies were performed on myometrial membrane and cytosolic preparations from rats which had been ovariectomized and subsequently received no hormonal treatment or had been treated with oestradiol, progesterone or combined oestradiol and progesterone. The β-adrenergic antagonist [125I]iodocyanopindolol and the unlabelled competing agonist, isoprenaline, were used in the present studies. Hormonal treatment had no effect on the concentration of β-adrenergic binding sites in the myometrium (i.e. the number of membrane-bound and cytosolic binding sites per mg protein). However, significant changes were found in the total number of binding sites; these were associated with the hormone-induced tissue hypertrophy. In myometrium from ovariectomized-alone rats, approximately 50% of β-adrenergic binding sites were present in the cytosolic fraction. Oestradiol treatment, either on its own or in combination with progesterone, resulted in the translocation of binding sites to the cell membrane. However, in the absence of progesterone only 33% of the membrane-bound binding sites bound the β-adrenergic agonist, isoprenaline, with a high affinity, suggesting that the majority of these membrane-bound binding sites represented non-functional β-adrenoceptors. Progesterone treatment resulted in a doubling in number of the high affinity membrane-bound receptors. As a result of our findings we propose that oestrogen and progesterone act together in regulating β-adrenoceptor function: it is proposed that oestrogens increase the number of β-adrenergic binding sites associated with the cell membrane while progesterone promotes the coupling of these binding sites to their effector mechanisms thus leading to an increase in the number of functional β-adrenoceptors.

Journal of Endocrinology (1995) 147, 303–309