bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased insulin receptor number and insulin responsiveness in a chicken hepatoma cell line
Authors: Taouis M , Derouet M , Caffin J P , Simon J
Published: December 2008

Insulin receptor number and insulin responsiveness were compared in a chicken hepatoma cell line (LMH) and in normal chicken hepatocyte (cHep) cells cultured in the same conditions. LMH cells expressed two- to threefold more insulin receptors than cHep cells, without significant changes in affinity. The tyrosine kinase activity of solubilized and lectin (lentil+wheat germ agglutinin; WGA)-purified LMH receptors was higher than that of cHep receptors. The ATP hydrolytic activity previously observed in WGA-purified receptors from chicken liver membranes was also present in WGA-purified receptors from cultured cHep cells. This unidentified membrane-associated ATPase was absent from LMH membrane-solubilized material and therefore from WGA-purified LMH insulin receptors. Finally, LMH cells incorporated at least tenfold more amino isobutyric acid than cHep cells in the absence of insulin and were more responsive to insulin. The enhanced basal amino acid transport of LMH cells was most probably the consequence of their proliferative activity. The enhanced insulin responsiveness of LMH cells can be accounted for, at least in part, by one or several of the modifications presently demonstrated in LMH cells when compared with normal cultured hepatocytes: increased insulin receptor number and tyrosine kinase activity and possibly the loss of the membrane-associated ATPase.

Journal of Endocrinology (1994) 140, 119–124
Low intrathyroidal iodine concentration in non-endemic human goitres: a consequence rather than a cause of autonomous goitre growth
Authors: Aeschimann S , Buergi U , Wagner H E , Kaempf J , Lauber K , Studer H
Published: December 2008

Iodine may have an inhibitory and, in some circumstances, a stimulatory effect on thyroid follicular cell growth. Exogenous iodine deficiency causes the growth of endemic goitres and it has been claimed that low intrathyroidal iodine stores stimulate growth. On the other hand, the role of iodine, if any, in regulating the growth of human nodular goitres exposed to an ample supply of iodine has not been studied systematically. Very few data on intrathyroidal iodine concentration in this type of goitre are available.

In the present work we have investigated total iodine content in 24 samples from 11 clinically and histomorphologically well-defined fast and autonomously growing human nodular goitres from a non-endemic area. Iodine was fractionated into thyroglobulin-iodine and non-thyroglobulin-iodine. The regional distribution of intrathyroidal iodo-compounds was also assessed in three goitres.

Total iodine concentration, as well as its sub-fractions, i.e. thyroglobulin-iodine and non-thyroglobulin-iodine, were significantly lower than in normal thyroids. Furthermore, there was large inter- and intraindividual heterogeneity of all iodo-compounds as well as of thyroglobulin. Total iodine concentration varied by a factor of almost 40 between different goitre samples and by a factor of 20 between samples taken from the same goitre. Total non-thyroglobulin-iodine, the only fraction comprising possible cell growth-regulating iodocompounds, varied by a factor of >60 between different goitres and by a factor of >6 between different samples of the same goitre.

The low iodine concentration in all our goitre samples did not differ from values reported in the literature for endemic iodine-deficient goitres. Since all goitres studied here were actively growing while exposed to an ample supply of iodine, iodine shortage cannot be a primary and causal factor for the growth of this type of sporadic goitre. Rather, the low concentration and the large inter- and intraindividual heterogeneity of all iodocompounds appear to be secondary incidental events well explained by the recently developed concept of autonomous thyroid growth.

Journal of Endocrinology (1994) 140, 155–164
Glucagon binding to hepatocytes isolated from two teleost fishes, the American eel and the brown bullhead
Authors: Navarro I , Moon T W
Published: December 2008

We have characterized the specific binding of glucagon in hepatocytes isolated from two teleost species, the American eel (Anguilla rostrata) and the brown bullhead (Ictalurus nebulosus). Specific glucagon binding was 9·3 and 10·7% in bullhead and eel hepatocytes respectively, after a 2-h incubation at 12 °C. Curvilinear Scatchard plots suggest the presence of two classes of binding sites with apparent dissociation constants (Kd) of 1·97 nm (high affinity) and 17·3 nm (low affinity) for bullhead and 2·68 and 22·9 nm for eel cells. The number of high-affinity binding sites per cell was significantly higher in the eel (10 413) than in the bullhead (3811). The number of high-affinity insulin-binding sites was approximately two times higher than that for glucagon in bullheads and the opposite in the eel hepatocytes. In competition experiments, insulin did not displace 125I-labelled glucagon binding in the hepatocytes of either species, while glucagon-like peptide-1(7–37) (GLP-1) displaced glucagon but only at high concentrations, suggesting separate glucagon- and GLP-1-binding sites. The rate of dissociation of hepatocyte-bound 125I-labelled glucagon was similar for both species. Preincubation of hepatocytes in 100 nm glucagon decreased the number of high-affinity glucagon-binding sites by approximately 55% in both species, while the Kd values remained unchanged. Glucagon bound to the cell surface is internalized by fish hepatocytes. These properties indicate that the glucagon binding to hepatocytes of these two teleost species is similar to that reported for mammalian hepatocytes.

Journal of Endocrinology (1994) 140, 217–227
Inhibition of progesterone receptor function results in loss of basic fibroblast growth factor expression and stromal cell proliferation during uterine remodelling in the pregnant rat
Authors: Rider V , Psychoyos A
Published: December 2008

Recent studies suggest that hormonal control of uterine cell proliferation may be moderated by polypeptide growth factors. It remains to be determined, however, whether growth factors cause or are the consequence of hormone action. Basic fibroblast growth factor (bFGF) has been shown to influence cell proliferation and differentiation of a variety of mesoderm-derived cells. To elucidate the regulatory mechanisms controlling stromal cell proliferation and differentiation required for embryo implantation further, immunohistochemical localization of the progesterone receptor and bFGF have been studied. The cell-specific distribution of these proteins was determined in the rat uterus during early pregnancy and after injection of the progesterone receptor antagonist mifepristone (RU 486) at days 1 and 2 post coitum (p.c.) to block implantation. Cell division was restricted to luminal and glandular epithelial cells in pregnant and RU 486-treated rats at day 3 p.c. At day 4 of pregnancy, cell proliferation switched from the epithelia to the stroma in pregnant rats, but after RU 486 treatment division of stromal cells was inhibited significantly (P < 0·05). Progesterone receptor distribution was altered and bFGF was absent in RU 486-blocked stromal cells. Expression of bFGF in luminal and glandular epithelial cells, however, was insensitive to the effects of progesterone receptor antagonism. bFGF content was stimulated in the luminal epithelium and in decidual cells by the implanting embryo. These results indicate that repression of progesterone receptor function in early pregnancy results in a cell-specific loss of bFGF from stromal cells and inhibition of their proliferation. The results further suggest that the regulation of endometrial cell bFGF content is modulated at the site of implantation by the embryo.

Journal of Endocrinology (1994) 140, 239–249
Insulin-like growth factor-binding protein-1 is correlated with low density lipoprotein cholesterol in normal subjects
Authors: Hopkins K D , Lehmann E D , Parker J R , Gosling R G
Published: December 2008

Insulin-like growth factor-I (IGF-I) has been inversely associated with low-density lipoprotein (LDL) cholesterol in normal women with slightly elevated cholesterol levels and hypothyroid women. More than 95% of IGF-I circulates bound to binding proteins (IGFBPs); of these IGFBP-1 is of particular interest as it is inversely regulated by insulin and is thought to inhibit the action of IGF-I and IGF-II. We examined the relationship between IGFBP-1 and LDL cholesterol in 41 healthy adult subjects.

LDL cholesterol correlated with the body mass index (r=0·40, P<0·01), sex (r=0·51, P<0·001) and IGFBP-1 levels (r=0·36, P<0·02). LDL cholesterol did not correlate with age (r=0·25, P=not significant) or IGF-I (r=0·06, P=not significant). Upon multivariate regression analysis, sex, body mass index and IGFBP-1 were all independent predictors of LDL cholesterol (all P<0·05).

Elevated IGFBP-1 levels have been associated with an inhibition of serum IGF-I bioactivity in children with insulin-dependent diabetes. IGFBP-1 also appears to inhibit IGF-I hexose-stimulated uptake. IGFBP-1 may also be inhibiting the effect of IGFs on the cellular metabolism of LDL cholesterol.

Journal of Endocrinology (1994) 140, 521–524
ACTH STIMULATES MELANOGENESIS IN CULTURED HUMAN MELANOCYTES
Authors: Hunt G. , Todd C. , Kyne S. , Thody A.J.
Published: December 2008

While ACTH is known to induce skin pigmentation in man, its effects on cultured human melanocytes have not been investigated. Using a culture system free of artificial mitogens, we report for the first time that ACTH stimulates melanogenesis in cultured human melanocytes. While ACTH, α-MSH and the synthetic α-MSH analogue Nle4DPhe7α-MSH all stimulate the activity of tyrosinase, the rate limiting enzyme in melanogenesis, and all produce a 50% increase in the melanin content of the cells at a concentration of 10−8-10−7 mol/l, the shapes of the dose response curves differ: those for the MSH peptides are sigmoidal while those for ACTH are biphasic. In addition, human melanocytes are able to respond to concentrations of ACTH comparable with physiological plasma levels. We suggest that ACTH may be relatively more important than α-MSH as a pigmentary hormone in man and could have a physiological role in skin pigmentation.
Periovulatory LHRH, LH and FSH secretion in cyclic rats treated with RU486: effects of exogenous LHRH and LHRH antagonist on LH and FSH secretion at early oestrus
Authors: Sánchez-Criado J E , Hernandez G , Bellido C , Gonzalez D , Tébar M , Diaz-Cruz M A , Alonso R
Published: December 2008

The antiprogesterone RU486 injected on the morning of pro-oestrus blunts the preovulatory secretion of LH and FSH and abolishes the secondary secretion of FSH during oestrus without affecting ovulation in the rat. To ascertain whether the secretion of LHRH is involved in these effects, we studied the effects of RU486 (4 mg/0·2 ml oil), given s.c. at 0800 h on pro-oestrus, on LHRH secretion into the pituitary stalk blood vessels and on peripheral plasma concentrations of LH and FSH at 1800 h on pro-oestrus and 0200 h on oestrus. Furthermore, we determined the effects of an s.c. injection of 1 mg of an LHRH antagonist (LHRH-A; ORG30276) at 2000 h on pro-oestrus and those of an i.p. injection of 100 ng LHRH (Peninsula 7201) at 0100 h on oestrus on serum concentrations of LH, FSH and oestradiol at 0200 h on oestrus in oil- and RU486-treated rats.

RU486 decreased LHRH secretion at 1800 h on prooestrus while this was increased at 0200 h on oestrus. While the reduction of preovulatory LHRH secretion in RU486-treated rats coincided with a reduction in both LH and FSH surges during the evening of pro-oestrus, the increased LHRH secretion during the early hours of oestrus was only accompanied by an increased concentration of LH. An injection of LHRH stimulated, while that of LHRH-A inhibited serum concentrations of LH at 0200 h on oestrus in both oil- and RU486-treated rats. An injection of LHRH-A had no effect on FSH concentration at 0200 h on oestrus in either oil- or RU486-treated rats. On the contrary, exogenous LHRH increased FSH concentration at 0200 h on oestrus only in oil-treated rats.

The results indicate that, in the rat, progesterone secretion during the afternoon and evening of pro-oestrus enhances preovulatory LHRH and suppresses LHRH release during early oestrus into the pituitary stalk blood vessels on the afternoon of pro-oestrus and during early oestrus respectively. While the secretion of LH during early oestrus is blunted by progesterone and entirely coupled to LHRH secretion, the secondary secretion of FSH during oestrus is not dependent on endogenous LHRH and at the same time is completely dependent on the actions (direct and/or indirect) of progesterone.

Journal of Endocrinology (1994) 141, 7–14
Production of anti-idiotypic antibodies resembling bovine somatotrophin by active immunization of lactating cows
Authors: Schalla C L , Roberge S , Wilkie B N , McBride B W , Walton J S
Published: December 2008

Anti-idiotypic antibodies produced in lactating cows by immunization with rabbit antibodies raised against bovine somatotrophin (bST) were evaluated for bST-like immunoactive and biological activities. Twenty New Zealand White rabbits were immunized against bST. Serum was purified using protein A–Sepharose CL-4B and bST–Sepharose 4B affinity chromatography to yield specific anti-bST immunoglobulin G (IgG). Twenty-four lactating cows were allocated to a randomized complete block design and were immunized with either: (1) rabbit anti-bST (n=12) or (2) non-specific rabbit IgG (n=12, control). Cows were immunized starting at day 68 of lactation with 800 μg antigen emulsified with Freund's complete adjuvant and 1 mg Quil A administered by i.m. injections. Repeated immunizations of 800 μg antigen in Freund's incomplete adjuvant and 1 mg Quil A followed after 3 weeks and then every 5 weeks throughout lactation. Serum samples were collected twice weekly and were analysed for anti-rabbit IgG titre and immunoactive bST concentration by radioimmunoassay. All cows developed antibodies against rabbit IgG by the second and third immunizations. With rising titres, immunoactive bST concentrations increased in cows treated with anti-bST following each of the six repeated immunizations to 4·7±3·3, 10·0±4·2, 12·0±4·8, 17·3±6·7, 24·0±10·0 and 36·3±20·4 ng/ml (mean±s.e.m.) compared with controls (0·81±0·09 ng/ml, overall mean±s.e.m.). To assess the biological activity of these bST anti-idiotypic antibodies, milk yield and serum insulin-like growth factor-I (IGF-I) concentrations were analysed in all cows and a subset of six cows per treatment respectively. Milk production and IGF-I concentrations were unaffected by anti-bST immunization.

Journal of Endocrinology (1994) 141, 203–208
Evidence for a primary involvement of somatostatin in clonidine-induced growth hormone release in conscious rats
Authors: Lanzi R , Lapointe M , Gurd W , Tannenbaum G S
Published: December 2008

The GH-releasing activity of the α2-adrenergic agonist clonidine has been extensively studied in the rat, but the mechanism(s) by which clonidine stimulates GH release remains controversial. In the present study, we examined the effects of various doses of clonidine on spontaneous pulsatile GH secretion in conscious rats, and tested the hypothesis that the GH-releasing activity of clonidine is mediated primarily by an inhibition of hypothalamic somatostatin (SRIF) release. In the first experiment, free-moving adult male rats were given either saline or various doses of clonidine i.v. (30, 50 and 125 μg/kg) at times of spontaneous peaks (1100 h) and troughs (1300 h) in the GH rhythm. Clonidine, at all doses tested, failed to stimulate GH release when administered at the time of a spontaneous peak. In contrast, injection of clonidine at trough times (when SRIF tone is high) consistently augmented plasma GH levels (mean ± s.e.m. integrated GH release; 30 μg/kg, 1843·0±484·0; 50 μg/kg, 1469·0± 490·3; 125 μg/kg, 1675·6 ± 513·4 vs 201·3 ± 100·1 ng/ml per 45 min in saline-injected controls; P<0·05 or less). No significant regression was observed between increasing doses of clonidine and GH release. In the second experiment, i.v. administration of 30 μg clonidine/kg during a GH trough period, 30 min prior to GH-releasing factor (GRF) challenge, significantly potentiated the GH response to GRF compared with rats given saline (7218·7 ±806·6 vs 4206·9 ± 1068·1 ng/ml per 30 min; P<0·05). Clonidine treatment, at all doses tested, resulted in hyperglycaemia and behavioural effects. These results showed that: (1) clonidine is not a potent GH secretagogue in the rat; (2) when administered i.v., clonidine exerts a maximal GH-releasing activity already at the dose of 30 μg/kg; and (3) clonidine-induced GH release in the rat occurs mainly through an inhibition of hypothalamic SRIF release rather than by stimulating GRF secretion.

Journal of Endocrinology (1994) 141, 259–266
Preferential expression of long form prolactin receptor mRNA in the rat brain during the oestrous cycle, pregnancy and lactation: hormones involved in its gene expression
Authors: Sugiyama T , Minoura H , Kawabe N , Tanaka M , Nakashima K
Published: December 2008

The mRNA species for prolactin receptor (PRL-R) isoforms, long and short form PRL-Rs, were estimated by the reverse transcription-polymerase chain reaction method in the rat brain (cerebrum) during the oestrous cycle, pregnancy and lactation. The levels of long form PRL-R mRNA increased at pro-oestrus and oestrus, at the same time as serum prolactin levels increased, whereas the mRNA level of short form PRL-R was relatively unchanged. Long form PRL-R mRNA expression was also markedly increased in the brain at mid- and late gestation, and this elevated mRNA level was maintained during the period of lactation. In contrast, basal levels of short form PRL-R mRNA were also maintained throughout these periods of gestation and lactation. Ovariectomy moderately reduced brain mRNA levels of both long and short form PRL-R from the levels of those in control dioestrous rats, and hypophysectomy further suppressed them to the lowest levels. Administration of oestradiol valerate (E2V) or 17α-hydroxyprogesterone caproate (17OHPC) to ovariectomized rats resulted in dramatic increases in long form PRL-R mRNA levels in the brain, whereas no significant increase in short form PRL-R mRNA was observed. In rats which were ovariectomized and hypophysectomized, the administration of 17OHPC, rat prolactin or rat GH partially restored the brain level of long form PRL-R mRNA but not short form PRL-R mRNA. E2V, on the other hand, had no effect on the expression of brain PRL-R mRNAs in these hypophysectomized rats, suggesting that the stimulatory effect of E2V on long form PRL-R mRNA expression in ovariectomized rats was mediated by an enhanced secretion of a pituitary hormone, prolactin. These results suggest that the expression of long form PRL-R mRNA in the rat brain is directly induced by progesterone, prolactin or GH during the oestrous cycle, pregnancy and lactation.

Journal of Endocrinology (1994) 141, 325–333
Rapid changes in plasma concentrations of insulin-like growth factor-I (IGF-I), IGF-II and IGF-binding proteins during anaesthesia in young sheep
Authors: Lord A P D , Read L C , Owens P C , Martin A A , Walton P E , Ballard F J
Published: December 2008

Halothane anaesthesia in young sheep results in greatly increased plasma binding capacity for radiolabelled insulin-like growth factor (IGF), as demonstrated using size-exclusion chromatography. Most of the increased binding was at an estimated molecular mass range of 30–50 kDa, with a smaller increase evident at 130–150 kDa. These changes were not evident in control animals which had food withheld for the same period. The progressive increase in plasma radioligand binding during anaesthesia was the net result of a rise in circulating levels of a 29–31 kDa IGF-binding protein (IGFBP), as shown by ligand blotting, and declining plasma concentrations of IGF-I and IGF-II. Recovery from anaesthesia was accompanied by the restoration of plasma IGFs and the IGFBP towards pre-anaesthesia concentrations. The induced IGFBP was provisionally identified as IGFBP-1 because it bound anti-IGFBP-1 antiserum but not antibodies against IGFBP-2, IGFBP-3 or IGFBP-4. The elevation of plasma IGFBP-1 immunoreactivity was associated with reduced concentrations of glucose and insulin, the regulators of IGFBP-1 in humans and rats. These results suggest that IGF experiments that require anaesthesia but assume that the anaesthetised state is representative of conscious sheep should be reassessed. A similar situation may occur with other mammalian species.

Journal of Endocrinology (1994) 141, 427–437
Distribution of the adrenocortical inner zone antigen
Authors: Ho M M , Barker S , Vinson G P
Published: December 2008

Previous studies using a mouse monoclonal antibody (IZAb) have identified inner zone-specific antigens (IZAg 1 and 2) in the rat adrenal cortex. The expression of IZAgl is enhanced by dibutyryl-cyclic AMP or ACTH in vitro and by in vivo ACTH treatment. These studies also suggest that IZAg may be involved in steroidogenesis in rat adrenals.

Using sensitive detection methods, the distribution of IZAg in adrenals from other species and in other rat tissues was studied. Pig and rabbit adrenals expressed an IZAb-immunoreactive protein with molecular mass identical with that of IZAg1, but no immunoreactivity was detected in bovine, guinea-pig or mouse adrenals. In the rabbit adrenal, as in the rat, IZAb bound only to zonae fasciculata/reticularis cells. However, the whole adrenal cortex in the pig immunoreacted with IZAb. Although immunofluorescence was observed in human adrenal sections, predominantly in the zona reticularis, no significant immunoreactive protein band was detected by immunoblot analysis. Apart from the zonae fasciculata/reticularis in the adrenal gland, an IZAb-immunoreactive protein with a molecular mass of 26 000 Da, corresponding to IZAg1, was also found in rat hepatocytes, renal tubules, ovary (corpus luteum, interstitial cells, theca interna of mature follicles) and Leydig cells.

The observations suggest that IZAg may be involved in the processes of biosynthesis, metabolism and/or excretion of steroid hormones.

Journal of Endocrinology (1994) 141, 459–466
Neonatal monosodium glutamate treatment alters both the activity and the sensitivity of the rat hypothalamo-pituitary-adrenocortical axis
Authors: Larsen P J , Mikkelsen J D , Jessop D , Lightman S L , Chowdrey H S
Published: December 2008

We have investigated the effects of monosodium glutamate (MSG) lesioning of the arcuate nucleus on both central and peripheral components of the hypothalamo-pituitary-adrenocortical (HPA) axis under basal conditions and under acute and chronic stress. Plasma ACTH levels were lower in MSG-lesioned rats (27 ± 7 pg/ml) compared with controls (71 ± 18 pg/ml) while corticosterone levels were elevated (523 ± 84 ng/ml compared with 176 ± 34 ng/ml). Quantititative in situ hybridization histochemistry revealed that corticotrophin-releasing factor mRNA levels in the medial parvocellular part of the hypothalamic paraventricular nucleus were significantly lower in MSG-treated rats. MSG lesioning resulted in an enhanced response of corticosterone to restraint stress (1309 ± 92 ng/ml compared with 628 ± 125 ng/ml in sham-lesioned animals), while ACTH responses to restraint stress in MSG-lesioned and sham-MSG groups were not significantly different (160 ± 24 pg/ml and 167 ± 24 pg/ml respectively). These data suggest that MSG-lesioned rats have an increased adrenocortical sensitivity. In rats subjected to the chronic osmotic stimulus of drinking 2% saline for 12 days, plasma ACTH levels were significantly reduced (15 ± 5 pg/ml) and the ACTH and corticosterone responses to restraint stress were eliminated. ACTH levels were also reduced in MSG-treated animals given 2% saline and the ACTH response to acute stress remained absent in these animals. However, a robust corticosterone response to restraint stress was observed in saline-treated MSG-lesioned rats. These data demonstrate that MSG lesioning results in elevated basal and stress-induced plasma corticosterone, and restores the adrenocortical response to stress which is absent in chronically osmotically stimulated rats. The evidence is consistent with the suggestion that MSG lesions a pathway involved in tonic inhibition of the HPA axis. In addition, the adrenocortical sensitivity to ACTH and other secretagogues may be increased in MSG-treated animals.

Journal of Endocrinology (1994) 141, 497–503
Transfer of insulin-like growth factor (IGF)-I from blood to intestine: comparison with IGFs that bind poorly to IGF-binding proteins
Authors: Lord A P D , Martin A A , Ballard F J , Read L C
Published: December 2008

The net transfer of 125I-labelled insulin-like growth factor (IGF)-I from the blood to the distal small intestine was measured in anaesthetized lambs using a non-recirculating vascular-perfused intestine. To determine whether IGF-binding proteins (IGFBPs) reduce net IGF transfer, radio-labelled IGF-I was compared with two analogues, des(1–3)IGF-I and LR3IGF-I, which show reduced affinity for IGFBPs. Radiolabelled IGF-I, des(1–3)IGF-I or LR3IGF-I (1 ng/ml plasma) was infused for 45 min into the arterial supply of a 10 cm intestinal segment, either in the absence of added unlabelled peptide (high specific activity) or in the presence of a 100-fold excess of unlabelled homologous peptide (low specific activity) to achieve different proportions of free and complexed peptide. Very little degradation of radiolabelled peptides was detected in plasma, with 3–10% degradation in the intestinal tissue. Less than 5% of radiolabelled IGF-I remained as free peptide in the efferent venous plasma of the perfused segment at both specific activities. Bound radio-labelled IGF-I was found by size-exclusion chromatography mainly in the 30–50 kDa region, with a smaller proportion in the 150 kDa peak. The net intestinal transfer of IGF-I, calculated as the sum of the proportions of infused tracer recovered from intestinal tissue, luminal contents and lymph, was 3·46 ± 0·22% (s.e.m.) and 3·49 ± 0·93% when infused at high and low specific activities respectively. The analogues differed from IGF-I with up to ninefold higher concentrations of free radio-labelled peptide in venous plasma of the perfused intestinal segment, and corresponding decreases in binding to the 30–50 kDa binding proteins. Notwithstanding these marked differences in the plasma levels of free peptide, net intestinal transfer was very similar for the three peptides, as was the extent of degradation in the intestinal tissue. The lack of correlation between binding to 30–50 kDa binding proteins and net intestinal transfer suggests that association with 30–50 kDa plasma binding proteins is not a rate-limiting determinant of net IGF transfer to intestinal tissue.

Journal of Endocrinology (1994) 141, 505–515
Internalisation of the type I angiotensin II receptor (ATI) and angiotensin II function in the rat adrenal zona glomerulosa cell.
Authors: Vinson G. P. , Ho. M. M. , Puddefoot J.R. , Teja R. , Barker S.
Published: December 2008

Little is known about the cellular localisation of the angiotensin II (AII) type 1 receptor (ATI) in the rat adrenal glomerulosa cell, but some studies have suggested that receptor internalisation and recycling may occur.

Using a specific monoclonal antibody (6313/G2) to the first extracellular domain, we show here that most of the receptor is internalised in the unstimulated cell. When viable glomerulosa cells are incubated with 6313/G2, the receptor is transiently concentrated on the cell surface, and aldosterone output is stimulated. This stimulated output is enhanced by neither threshold nor maximal stimulatory concentrations of All amide, although the antibody does not inhibit All binding to the receptor. Conversely, the stimulatory actions of the antibody and those of ACTH are additive.

The data suggest that recycling to the plasma membrane is constitutive, or regulated by unknown factors. Retention of the ATI receptor in the membrane is alone enough to allow sufficient G protein interaction to generate maximal stimulatory events.
Angiotensin II-mediated catecholamine release during the pressor response in rats
Authors: Butler D G , Butt D A , Puskas D , Oudit G Y
Published: December 2008

Angiotensin II (ANG II)-mediated catecholamine release and its possible contribution to the pressor response was assessed in baroreceptor-denervated rats.

Neonatal male Sprague-Dawley rats were injected with the sympatholytic drug, guanethidine monosulphate (50 mg/kg s.c., 6 days/week) for 40 days. Plasma catecholamine concentrations were measured using a 3H-radioenzymatic assay as follows: (a) before and 30 s after the injection of saline or ANG II (79·3 pmol/kg i.v.), at the peak of the pressor response, then 50 s and 80 s thereafter, in guanethidine-treated (GUAN) and saline-injected (SHAM) rats, and (b) before and after adrenalectomy (ADX), following the same time-sequence for ANG II as in (a). Peak pressor responses to graded doses of ANG II (6·6, 26·4, 53·0 and 79·3 pmol/kg i.v.) were measured in GUAN+ADX and ADX rats. Destruction of peripheral sympathetic nerves was confirmed by measurements of plasma noradrenaline (NA), adrenaline (AD) and dopamine (DA) concentrations and by changes in pressor responses and heart rates following i.v. doses of tyramine.

ANG II induced significantly (P<0·05) greater pressor responses in GUAN+ADX rats than in ADX rats, especially after the 53·0 and 79·3 pmol/kg doses. Plasma AD concentrations increased within seconds after the pressor response to ANG II in both GUAN and SHAM rats but there was no change in plasma NA or DA concentrations (P<0·05). ANG-II-mediated AD release from the adrenal medulla may contribute to the overall pressor action of the peptide.

The vasculature became more sensitive to ANG II at a time when NA and DA depletion occurred following sympathectomy and/or adrenalectomy. This heightened sensitivity to ANG II was not due to a decrease in circulating ANG II in sympathectomized rats because even though plasma renin activity fell from 6·54 ±0·52 to 3·77 ±0·26 ng ANG I/ml per h it remained within the normal range.

Journal of Endocrinology (1994) 142, 19–28
Human growth hormone augmentation of epidermal growth factor binding sites on rat granulosa cells
Authors: Hattori M-A , Shinohara Y , Yoshino E , Kanzaki M , Kojima I , Horiuchi R
Published: December 2008

The effect of human GH (hGH) on the regulation of epidermal growth factor (EGF) receptor was investigated during differentiation of FSH-treated rat granulosa cells, which has been reported to be mediated by a cAMP-dependent mechanism. By measuring the binding of [125I]iodo-EGF to the intact cells, FSH was shown to cause increases in the number of EGF binding sites after culture for 72 h. When granulosa cells were cultured with hGH, the number of FSH-induced EGF binding sites was augmented, with a half-maximal effect at about 10 μg hGH/l and a maximal stimulatory concentration of 100 μg/l. The stimulatory effect of hGH was absolutely dependent on insulin which by itself showed stimulatory effects on EGF binding sites. Scatchard analysis of EGF binding sites indicated that treatment with hGH increased the number of EGF binding sites (17 200 sites/cell after treatment with FSH; 31 700 sites/cell after FSH plus hGH), but did not alter the binding affinity. The augmentation was observed after culturing for 48 h and increased progressively with time, reaching 280% of the level after FSH treatment by 120 h. Although progesterone synthesis was increased by hGH, the markers of cell differentiation such as cAMP synthesis and LH binding sites were suppressed, indicating hGH inhibition of the cAMP-mediated signal. The action of hGH on the EGF binding sites was not accompanied by cell proliferation. These findings indicate that hGH has a novel action on the regulation of rat granulosa cell EGF binding sites and that the granulosa cell may possess both cAMP-dependent and -independent mechanisms for expression of EGF binding sites.

Journal of Endocrinology (1994) 142, 69–75
Modulation of arginine vasotocin secretion in chicks by dehydration during embryogenesis
Authors: Kisliuk S M , Grossmann R
Published: December 2008

The influence of low humidity during incubation (LHI) on arginine vasotocin (AVT) secretion in male and female White Leghorn chicken embryos and chicks was investigated. LHI embryos were incubated from day 8 (E8) to E18 at a relative humidity of 32–35%, while control embryos were incubated at 58–62%. In the control groups, plasma AVT gradually increased from E15 to E18, increased sharply during hatching and returned to the El8 level within 4 h. LHI did not alter the level of AVT until E18. LHI E19 males had concentrations of AVT twice as high as those of control males (39 ± 3·9 vs 15 ± 1·6 pmol/l, P<0·001). Augmentation persisted during hatching and 4 h afterwards. In LHI females additional elevation reached significant levels only at 4 h after hatching (58 ± 13 vs 16 ± 1·7 pmol/l, P<0·01). Deprivation of water caused an increase in plasma sodium concentrations in the 2-day-old chicks of the control groups, while no significant changes were observed in the LHI group. Deprivation of water together with a high environmental temperature caused an additional increase in AVT only in the LHI groups (42 ± 5·2 vs 22 ± 3·9 pmol/l, P<0·01 for males; 32 ± 3·4 vs 19 ± 2·8 pmol/l, P<0·01 for females). The results clearly showed that LHI leads to a more pronounced response of the AVT system on subsequent osmotic and non-osmotic challenges, especially in males. Embryonal activation of the AVT system probably helps the organism to cope with hatching and posthatching stresses.

Journal of Endocrinology (1994) 142, 153–160
Superoxide dismutase, catalase and glutathione peroxidase activities in the lymphoid organs of diabetic rats
Authors: Pereira B , Rosa L F B Costa , Safi D A , Bechara E J H , Curi R
Published: December 2008

The effect of alloxan-induced diabetes on CuZn- and Mn-superoxide dismutase (SOD), catalase and glutathione peroxidase (GPX) activities, as well as the content of thiobarbituric acid reactive substances (TBARs) were examined in rat lymphoid organs (mesenteric lymph nodes (MLN), thymus and spleen) and, for comparison, red and white muscle fibres. The capacity for generation of reduced equivalents was also evaluated by measuring the activities of glucose-6-phosphate dehydrogenase (pentosephosphate pathway – cytosol) and citrate synthase (Krebs cycle – mitochondria). Diabetes raised the capacity for the generation of reducing equivalents in the lymphoid organs: in the mitochondria of the thymus and spleen and in the cytosol of the mesenteric lymph nodes and thymus. In muscles, diabetes reduced CuZn-SOD activity in soleus and raised the activity in gastrocnemius, and depressed the activities of catalase in soleus and of glutathione peroxidase in both soleus and gastrocnemius. In relation to the lymphoid organs, the spleen showed a decrease in the antioxidant enzyme activities (except for glutathione peroxidase), whereas the thymus showed an increased level (except for Mn-SOD), and the MLN presented a reduction in Mn-SOD and catalase activities and an increase in GPX activity caused by diabetes. The content of TBARs in the tissues followed the changes in GPX activity inversely: i.e. a decrease in the lymphoid organs (except in the spleen) and an increase in the muscles of diabetic rats compared with the control group. All these changes found in diabetic rats were reversed by insulin treatment and were not modified by the normalization of glycaemia.

Journal of Endocrinology (1994) 142, 161–165
Growth hormone inhibition of lipogenesis in sheep adipose tissue: requirement for gene transcription and polyamines
Authors: Borland C A , Barber M C , Travers M T , Vernon R G
Published: December 2008

The chronic inhibitory effect of growth hormone (GH) on lipogenesis in sheep adipose tissue explants was investigated in an in vitro tissue culture system. In the absence of other hormones, GH caused a decrease in the rate of lipogenesis after 6 h of culture. In contrast, when lipogenesis was stimulated by the presence of insulin plus dexamethasone, GH again decreased lipogenesis but after a lag of at least 12 h.

Actinomycin D, an inhibitor of gene transcription, prevented the effect of GH on lipogenesis in both the absence and presence of insulin plus dexamethasone. Actinomycin D added to tissue previously incubated for 6 h in the presence of GH alone prevented further decline in lipogenesis over the next 5 h, suggesting that transcription of a short-lived mediator protein is required for the GH effect to occur.

An increase in ornithine decarboxylase activity was detected in explants exposed to GH, reaching a peak after 12 h incubation; this was prevented by actinomycin D. Methylglyoxal bis-(guanylhydrazone), an inhibitor of polyamine biosynthesis, partially alleviated the effect of GH on lipogenesis; this was reversed by addition of spermidine. However, spermidine did not reverse the effects of actinomycin D, implicating a short-lived protein in addition to ornithine decarboxylase in the action of GH.

In the absence of other hormones GH had no effect on either the expressed (initial) or total activity of acetyl-CoA carboxylase, but GH prevented the increase in both expressed and total activities of the enzyme induced by insulin plus dexamethasone. Varying lipolysis and fatty acid accumulation in adipose tissue by addition of adenosine deaminase plus indomethacin or bovine serum albumin to the culture medium had no effect on lipogenesis and these agents partly alleviated GH inhibition of lipogenesis. No effect of GH was found on the amount of glycerol released by cultured tissue. GH also had no effect on fatty acid esterification.

Thus the chronic inhibitory effects of GH on lipogenesis involve a protein with a very short half-life. The effect also requires polyamines but does not appear to involve changes in fatty acid concentrations in the cell. In addition GH appears to inhibit lipogenesis and to antagonise insulin-stimulation of lipogenesis by different mechanisms.

Journal of Endocrinology (1994) 142, 235–243
Immunohistochemical localization of intracellular progesterone and glucocorticoid receptors in the rabbit lung
Authors: Camacho-Arroyo I , Ruiz A , Gamboa-Domínguez A , Pérez-Palacios G , Cerbón M A
Published: December 2008

We have determined the presence and distribution of intracellular progesterone receptors (PRs) and glucocorticoid receptors (GRs) in the lung of adult female rabbits using immunohistochemistry. The effects of ovariectomy and administration of oestradiol benzoate (10 μg for 3 consecutive days) upon PR and GR immunoreactivity were also studied. The results demonstrated the presence of both steroid hormone receptors in the female rabbit lung. PR and GR immunoreactivity was predominantly nuclear and located in alveolar epithelial cells and various interstitial cells such as polymorphonuclear leucocytes. Tissue distribution of both receptors was similar in all cases. Oestradiol treatment induced a marked increase in the number of PR immunoreactive cells compared with intact and ovariectomized female animals. Neither ovariectomy nor oestradiol treatment modified the number of GR immunoreactive cells. The presence and localization of intracellular PRs and GRs in several lung cell types suggest that they may play an important role in mediating the effects of progesterone and glucocorticoids in various physiological processes in the rabbit lung. The data also indicated an oestrogen regulation of PRs in the rabbit lung.

Journal of Endocrinology (1994) 142, 311–316
On the origin of physiologically high ratios of urinary testosterone to epitestosterone: consequences for reliable detection of testosterone administration by male athletes
Authors: Dehennin L
Published: December 2008

Testosterone administration to male athletes can be safely detected in the vast majority of cases by the urinary excretion ratio of testosterone to epitestosterone glucuronides (TG/EG), which may not exceed 6. Some rare cases of physiologically high TG/EG ratios (between 6 and 12) are encountered; these may be attributed to a dysregulation of the testicular secretions of epitestosterone which is decreased, and of epitestosterone sulphate (ES) which is normal or increased. Impaired hydrolysis of circulating epitestosterone sulphate by deficiency of a specific sulphatase acting on 17α-sulphates must also be considered as a possible reason for the decreased availability of epitestosterone for hepatic glucuronidation. Urinary excretions of conjugates and metabolites of testosterone and epitestosterone (expressed in nmol/mmol creatinine) have been determined by gas chromatography-mass spectrometry associated with stable isotope dilution, in a reference population of 90 healthy male subjects and in 12 subjects with chronic TG/EG>4. Urinary excretion ratios such as TG/(EG+ES), EG/ES and TG/5-androstene-3β,17α-diol glucuronide are shown to be efficient criteria which allow discrimination between physiologically high and pharmacologically high TG/EG ratios. A simple oral loading test with deuterium-labelled epitestosterone demonstrates the difference between hepatic and total epitestosterone metabolism clearly, particularly in subjects with physiologically high TG/EG in comparison with subjects with normal TG/EG.

Journal of Endocrinology (1994) 142, 353–360
A novel hypothyroid 'growth-retarded' mouse derived from Snell's dwarf mouse
Authors: Yoshida T , Yamanaka K , Atsumi S , Tsumura H , Sasaki R , Tomita K , Ishikawa E , Ozawa H , Watanabe K , Totsuka T
Published: December 2008

This paper describes a novel mutant mouse that has been spontaneously derived from the Snell's dwarf (DW/J) mouse. It was named the 'growth-retarded mouse' because of a characteristic growth pause followed by the delayed onset of pubertal growth. The onset of the increase in pituitary GH content that normally occurs concomitant with pubertal growth was also delayed in the growth-retarded mice. The serum concentration of thyroxine was very low in these mice from the neonatal period through adulthood, and a supplement of tri-iodothyronine was effective in shortening the growth pause and commencing the suppressed pubertal growth. Histological and immunohistochemical studies revealed that the anterior pituitary gland of the growth-retarded mouse contains clustered unusual chromophobic cells which are not reactive to various antisera against anterior pituitary hormones and the gland becomes enlarged with age. Breeding data indicated that these characteristics of the mice show an autosomal recessive inheritance and the gene responsible was designated as 'grm'. Partial linkage analysis utilizing microsatellite polymorphism demonstrated that the grm gene does not identify with the lit or hyt genes. Based on comparison of the hormonal status and growth pattern between growth-retarded, dwarf and normal mice, we have suggested the existence of a mutual interaction, possibly positive feedback regulation, between the pituitary and thyroid glands, that develops or matures the hormonal network which is responsible for rapid somatic growth and metabolic changes at puberty in mice.

Journal of Endocrinology (1994) 142, 435–446
Placental production of human chorionic gonadotrophin α and β subunits in early pregnancy as evidenced in fluid from the exocoelomic cavity
Authors: Nagy A-M , Jauniaux E , Jurkovic D , Meuris S
Published: December 2008

Levels of human chorionic gonadotrophin (hCG) and of its free α and β subunits were measured using specific immunoradiometric assays in exocoelomic fluid (ECF) and maternal serum (MS) collected from five pregnant women at 6·6-8 weeks of gestation. Mean levels of hCG and its free subunits were significantly (P<0·001) higher in ECF than in MS: 3·5-fold for hCG, 600-fold for free αhCG and 38-fold for βhCG. There was no correlation between either hCG levels or levels of its free subunits in ECF and MS. On a molar basis, the quantity of free αhCG subunit expressed as a percentage of the total (free+combined) amount was 83% in ECF and 2·7% in MS (P<0·001). The amount of free βhCG subunit as a percentage of the total was 22% in ECF and 3·5% in MS (P<0·001). The ratio of the total amounts of α- and βhCG subunits amounted to 4·6 in ECF and 0·99 in MS (P<0·001).

The heterogeneity of hCG was further investigated by polyacrylamide gel electrophoresis followed by immunoblotting. Several bands with molecular mass ranging from 42 to 57 kDa, corresponding to hCG dimers, were immunodetected in ECF and MS with anti-αhCG and anti-βhCG monoclonal antibodies. A free 35 kDa βhCG immunoreactive band was found in ECF and MS. A free αhCG immunoreactive band was observed at 23 kDa in ECF and at 21 kDa in MS.

These findings suggest that the exocoelomic cavity is a reservoir where hCG and its subunits produced by trophoblast accumulate directly. The excess of a free heavy αhCG subunit in ECF supports the hypothesis that, during early pregnancy, there is an excess of αhCG over βhCG subunit secretion by the trophoblast.

Journal of Endocrinology (1994) 142, 511–516
Mechanisms of reproductive deficiency in male rats treated neonatally with a gonadotrophin-releasing hormone antagonist
Authors: Pinilla L , Garnelo P , Tena-Sempere M , Gaytan F , Aguilar E
Published: December 2008

It is well known that males injected neonatally with oestradiol or antiserum or antagonists (ANT) against gonadotrophin-releasing hormone (GnRH) show multiple reproductive disorders. In the present work, in males treated neonatally with GnRH-ANT, we have analysed: (1) whether the impairment of reproductive function can be blocked by simultaneous treatment with gonadotrophins, (2) the possible differences in the effects of GnRH-ANT injected before or after the proliferation of Sertoli cells which takes place between days 1 and 15 of age, and (3) the mechanism(s) for the increased FSH secretion observed in adulthood. Experimental designs included: administration of GnRH-ANT between days 1 and 16 or 15 and 30 of age, simultaneous administration of gonadotrophins and GnRH-ANT to neonatal males, and measurement of FSH secretion after orchidectomy or specific destruction of Leydig cells with ethylene dimethane sulphonate (EDS) in adult males treated neonatally with GnRH-ANT.

The principal new data presented in our studies are the following: (1) delayed puberty was observed not only in males injected neonatally with GnRH-ANT, but also in those injected with gonadotrophins or with GnRH-ANT and gonadotrophins, (2) the decreased fertility and increased FSH secretion observed in adult males treated neonatally with GnRH-ANT were normalized by simultaneous administration of GnRH-ANT and gonadotrophins, and (3) the increased FSH secretion in adult males treated neonatally with GnRH-ANT remained after EDS or orchidectomy, suggesting that mechanisms other than decreased inhibin secretion were involved in the increased secretion of FSH.

Journal of Endocrinology (1994) 142, 517–525