bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of thyroid hormone on coenzyme Q and other free radical scavengers in rat heart muscle
Authors: Mano T , Sinohara R , Sawai Y , Oda N , Nishida Y , Mokuno T , Kotake M , Hamada M , Masunaga R , Nakai A , Nagasaka A
Published: December 2008

Active oxygen species are reported to cause organ damage. This study was therefore designed to determine the behaviour of antioxidants and free radical scavengers so as to reveal changes in animals in the hyper- and hypothyroid state.

Levels of antioxidant factors (i.e. coenzyme Q (CoQ)10, CoQ9 and vitamin E) and free radical scavengers (catalase, glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD)) were measured in the heart muscles of rats rendered hyper- or hypothyroid by 4 weeks of thyroxine (T4) or methimazol treatment. Serum levels of CoQ9 and total SOD were also measured.

A significant reduction in CoQ9 levels was observed in the heart muscles of both hyper- and hypothyroid rats when compared with control hearts. There was no difference in serum CoQ9 levels in thyroid dysfunction when compared with control animals. Levels of vitamin E in the heart muscles of hyperthyroid rats were significantly increased, and there was no reduction in vitamin E levels in hypothyroid rats when compared with control hearts. GSH-PX levels in the heart muscle were reduced in hyperthyroid rats and increased in hypothyroid rats when compared with control hearts. However, there were no differences in catalase levels in heart muscle between hyper- and hypothyroid rats. The concentration of SOD in heart muscle was increased in hyperthyroid rats and was not decreased in hypothyroid rats compared with control rats, suggesting the induction of SOD by excessive production of O2−.

These data suggest that the changes in these scavengers have some role in cardiac dysfunction in the hyper- and hypothyroid state in the rat.

Journal of Endocrinology (1995) 145, 131–136
Peptide amidating activity and gastrin processing in the developing sheep pancreas
Authors: Kapuscinski M , Shulkes A
Published: December 2008

Gastrin is a regulator of both gastric acidity and gastrointestinal growth and is expressed transiendy in the neonatal ovine and human pancreas. C-terminal amidation of glycine extended gastrin (G-gly) to gastrin amide (G-amide) by peptidylglycine α-amidating mono-oxygenase (PAM) is the final processing step. To investigate the relationship between PAM and gastrin synthesis in the developing pancreas, we measured PAM activity and the concentrations of gastrins in ovine pancreatic extracts from 95 days of gestation onwards.

Pancreatic PAM activity was highest in the 95-day-old fetus (138 ±29 pmol/h/mg protein, mean ± s.e.m.) and decreased to 9·5 ±3·7 pmol/h/mg protein in the adult. The circulating enzyme was also highest in the youngest fetus (1840 ± 165 pmol/h/ml plasma) decreasing to approximately 50% in the 135-day-old fetus, with no further significant changes. The concentration of bioactive G-amide in the pancreas was 2·0 ±0·6 pmol/g at 95 days of gestation, 3·4 ± 0·9 pmol/g at 135 days and decreased to 0·7±0·1 pmol/g in the adult. The precursor G-gly followed a similar pattern but its concentration was less than 10% of G-amide. These results show that: (a) there are high levels of PAM activity in the ovine fetal pancreas and in the fetal circulation, (b) PAM activity is apparently not rate-limiting in the bioactivation of pancreatic gastrin and (c) the dual expression of both PAM and gastrin in the fetal pancreas is similar to that observed in peptide-secreting tumours of the adult.

Journal of Endocrinology (1995) 145, 137–142
Pancreatic changes in somatostatin content and receptor/effector system after intrapancreatic injection of 5,7-dihydroxytryptamine
Authors: Muñoz-Acedo G , Alvaro-Alonso I , Arilla E
Published: December 2008

To date, it is unknown whether intrapancreatic serotonergic nerves can influence pancreatic somatostatin (SS) content and the SS receptor/effector system in the exocrine pancreas. In this study, the intrapancreatic serotonergic nerves were chemically ablated by injecting a specific serotonin (5-HT) neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT), into the substance of the gland. Three days after the injection, the 5-HT-like immunoreactive levels in the pancreas were reduced by more than 85% whereas somatostatin-like immunoreactive levels had increased (86%). The number of SS receptors in the pancreatic acinar cell membranes of the 5,7-DHT-treated rats was also increased (72%). No significant differences were seen in basal or forskolin-stimulated adenylate cyclase (AC) enzyme activities in the control and the 5,7-DHT-treated groups. In spite of the increase in the number of SS receptors in the pancreatic acinar cell membranes of 5,7-DHT-treated rats, SS caused a significantly lower inhibition of AC activity in these membranes. This finding is related to the observed decrease of a 41 kD pertussis toxin-sensitive substrate, presumably the αi subunit of the guanine nucleotide inhibitory protein, in pancreatic acinar cell membranes 3 days after intrapancreatic 5,7-DHT administration when compared with the corresponding controls. The functions of pancreatic serotonergic nerves seem to be associated with enteropancreatic communication. These data together with the present results suggest that pancreatic SS content and the SS receptor/effector system in the exocrine pancreas may be regulated by enteropancreatic serotonergic nerve fibers and may participate in enteropancreatic reflexes.

Journal of Endocrinology (1995) 145, 227–234
Neuropeptide Y modulates the sensitivity of the rat adrenal cortex to stimulation by ACTH
Authors: Hinson J P , Cameron L A , Kapas S
Published: December 2008

Neuropeptide Y (NPY) has been identified in nerves supplying the adrenal cortex of several mammalian species, although its function in this tissue is unknown. The present studies, employing adrenocortical cells prepared by collagenase digestion, have shown that NPY, in the absence of other stimulants, has no effect on steroid secretion by the rat adrenal over a range of peptide concentrations (10−11 to 10 −6 mol/l). However, in the presence of physiological concentrations of ACTH, which are submaximal for the stimulation of aldosterone secretion, NPY (10−6 mol/l) significantly enhanced the secretion rate of aldosterone by rat zona glomerulosa cells in response to ACTH. This effect was specific to the rat zona glomerulosa as NPY had no effect on the response to ACTH in rat zona fasciculata cells. The effect of NPY appears to be biphasic, however, as NPY significantly attenuated the steroidogenic response to supramaximal ACTH concentrations: in rat zona glomerulosa cells the aldosterone response to 10 −8 mol ACTH/l was significantly inhibited by NPY. The effect of NPY on the ACTH response appeared to be mediated by changes in the cAMP response. NPY had no effect on the steroidogenic response to potassium ions (K+), but enhanced the response to angiotensin II. NPY (10 −6 mol/l) significantly stimulated inositol 1,4,5-trisphosphate (InsP3) production although this concentration of peptide had no effect on steroid secretion. The effects of NPY on InsP3 production were additive with those of angiotensin II. These results suggest that the role of NPY in the adrenal cortex may be to regulate the sensitivity of the zona glomerulosa to peptide stimulation.

Journal of Endocrinology (1995) 145, 283–289
Absence of the oxytocin-induced prostaglandin F2α secretory response in uterus from ovariectomized ewes and activation of the response in vitro
Authors: Sheldrick E L , Flick-Smith H C , Bendall D E , Flint A P F
Published: December 2008

Oxytocin-induced prostaglandin F2α (PGF2α) responses were measured in explants of uterus from ovariectomized ewes on the day of tissue collection or after culture for 72 h in the presence or absence of oestradiol-17β (100 nmol/l). Oxytocin receptor binding activity was 210 ±47 fmol [3H]oxytocin bound per mg protein in fresh tissue and 89 ± 24 and 90 ± 17 fmol/mg in tissue cultured with control medium or with oestradiol respectively (means ± s.e.m.).

PGF2α production during the hour following oxytocin administration to freshly collected tissue was 272 ± 77 ng/g/h compared with 193 ± 35 ng/g/h in the absence of oxytocin. These rates were 2789 ± 1085 and 353 ± 135 ng/g/h after culture for 72 h in control medium and 2022 ± 496 and 342 ± 134 ng/g/h after culture with oestradiol. Thus oestradiol had no effect on the culture-induced maturation of the PGF2α response. Short-term exposure to arachidonic acid (66 μmol/l) did not increase PGF2α production in fresh tissue but significantly increased basal but not oxytocin-induced PGF2α production after 72 h in culture (P<0·05). There was an absence of oxytocin-induced inositol phosphate turnover in fresh tissue but after culture concentrations of inositol mono-, bis- and trisphosphates were all significandy increased by oxytocin (P<0·005). Antisera directed against G-protein α sub-units αi3, αo, αq, α11 and the common β subunit, and prostaglandin H-synthase-1 detected proteins that were present before and after culture. Oestradiol had no effect on the presence or apparent concentrations of these proteins.

Journal of Endocrinology (1995) 145, 299–305
A mixture of the branched chain amino acids leucine, isoleucine and valine increases ovulation rate in ewes when infused during the late luteal phase of the oestrous cycle: an effect that may be mediated by insulin
Authors: Downing J A , Joss J , Scaramuzzi R J
Published: December 2008

The positive relationship between nutritional state and ovulation rate in sheep may involve the action of specific nutrients on gonadotrophin release. LH and FSH secretion is controlled in part by hypothalamic GnRH, which is in turn influenced by central adrenergic and serotonergic neuronal systems. In this experiment the branched chain amino acids (BCAAs) leucine, isoleucine and valine were examined for effects on LH and FSH secretion. A mixture of the three amino acids was infused into ewes for 5 days immediately before luteolysis, a time when nutritional effects on ovulation rate occur.

The infusion significantly increased ovulation rate without any associated increase in FSH or LH. However, the infusion did increase plasma insulin concentrations and this effect, together with the high levels of blood urea observed, suggests that these amino acids had increased the supply of energy substrates to the follicles. An increase in insulin-mediated glucose uptake by follicles could be the stimulus responsible for the increase in ovulation rate. The ability of the animal to utilize BCAAs for energy metabolism may be an important component of the ovulation responses to nutrition.

Journal of Endocrinology (1995) 145, 315–323
Anti-idiotypic antibody as an oestrogen mimetic: removal of Fc fragment converts agonist to antagonist
Authors: Sömjen D , Amir-Zaltsman Y , Gayer B , Mor G , Jaccard N , Weisman Y , Barnard G , Kohen F
Published: December 2008

Previous studies indicated that the anti-idiotypic antibody (clone 1D5) caused an increase in uterine creatine kinase (CK) activity when administered in vivo to immature female rats, indicating that the antibody has oestrogenic-like activity. It was, therefore, of interest to investigate the structural requirements of clone 1D5 to act as an oestrogen mimetic in an in vitro model system. In the present study, the effect of clone 1D5 and its proteolytic fragments, F(ab′)2, Fab′ and Fc on CK activity was examined in cultured skeletal cells having functional oestrogen receptor (ER). Incubation of female-derived calvaria cells or epiphyseal cartilage cells with clone 1D5 (8·33 nm) or oestradiol (E2) (30 nm) for 24 h caused a significant increase in CK activity, indicating that clone 1D5 acted as an agonist. On the other hand, incubation of male-derived calvaria cells devoid of a functional ER with clone 1D5 or E2 did not have any effect on CK activity. Incubation of female-derived calvaria cells with clone 1D5 and E2 did not result in any further increase in CK activity, whereas dihydrotestosterone (DHT) did not alter the response to clone 1D5. The CK response to clone 1D5, in female-derived calvaria cells was time- and dose-dependent and could be inhibited in a dose-dependent manner by the oestrogen antagonist tamoxifen. In contrast, the proteolytic fragments of clone 1D5, the F(ab′)2 dimer (12 nm) and the Fab′ monomer (24 nm), and the Fc fragment (28 nm) did not have E2-like activity in these cells. However, while the Fab′ monomer or the Fc fragment, as well as clone 1D5, did not affect the response of the female-derived calvaria cells to E2, the F(ab′)2 dimer acted like an antagonist and completely inhibited the stimulatory effect of E2 or 1D5, but was unable to block the stimulatory effect of DHT on CK in male-derived calvaria cells. Collectively, these results imply that a bivalent antibody is necessary for the observed physiological responses, and that the anti-idiotypic antibody can be converted from an agonist to an antagonist by removal of the Fc portion of the antibody molecule. Furthermore, the anti-idiotypic antibody has an oestrogenic-like effect inhibited by tamoxifen only in skeletal cells capable of responding to E2.

Journal of Endocrinology (1995) 145, 409–416
The inhibitory action of melatonin in the ovine pars tuberalis is not dependent on changes in plasma membrane potential
Authors: McNulty S , Schurov I L , Morgan P J , Hastings M H
Published: December 2008

Treatment of ovine pars tuberalis (oPT) cultures with forskolin activates adenylyl cyclase, leading to increased levels of cyclic AMP, activation of protein kinase A, phosphorylation of the calcium/cyclic AMP response-element binding protein and the increased synthesis and secretion of several proteins. Simultaneous treatment with melatonin inhibits or reverses these effects of forskolin. In the neonatal rat pituitary, the inhibitory effects of melatonin are mediated by changes in membrane potential.

This study therefore investigated whether the inhibitory action of melatonin in oPT cultures is also dependent on the modulation of plasma membrane potential. Treatment of cultures with the ionophore valinomycin selectively permeabilised the cell plasma membrane to potassium, thereby causing membrane hyperpolarisation. In cultures of oPT, valinomycin inhibited in a concentration-dependent manner (maximal effect 2 μm) the stimulatory action of forskolin (1 μm) on intracellular levels of cyclic AMP, indicating that the activity of adenylyl cyclase in this tissue is sensitive to hyperpolarisation of the plasma membrane. However, increasing the extracellular concentration of potassium from 5 mm to 100 mm, which would depolarise the plasma membrane, had no effect on the inhibitory action of melatonin (1 μm) in forskolin-stimulated cultures. This indicated that melatonin could be effective in cells with sustained depolarisation. To test directly whether integrity of the plasma membrane is essential for melatonin to inhibit adenylyl cyclase, cultures were treated with the cholesterol-chelating agent saponin (50 μg/ml). Saponin increased cellular permeability to trypan blue and enhanced the release of the cytoplasmic enzyme lactate dehydrogenase to the extracellular medium, demonstrating that cell plasma membranes had been permeabilised, thereby abolishing membrane polarity. In cultures pretreated with saponin there was a tendency for levels of cyclic AMP to be reduced. However, permeabilisation did not block the forskolin-stimulated increases in cyclic AMP levels nor did it alter the ability of melatonin to inhibit the production of cyclic AMP in forskolin-stimulated cultures.

This study demonstrated that, while it is possible to inhibit the stimulatory actions of forskolin in the oPT by increasing the permeability of cells to potassium and thereby hyperpolarising them, melatonin is able to inhibit cyclic AMP in permeabilised cells and so can act independently of changes in membrane potential.

Journal of Endocrinology (1995) 145, 471–478
The effect of acute immuno-neutralisation of inhibin in ewes during the early luteal phase of the oestrous cycle on ovarian hormone secretion and follicular development
Authors: Campbell B K , Gordon B M , Tsonis C G , Scaramuzzi R J
Published: December 2008

Ewes with ovarian autotransplants received either inhibin antiserum (10 ml i.v. raised in sheep against recombinant 32 kDa human inhibin; n=6) or sheep serum (10 ml i.v.; n=5) on day 3 of the luteal phase with additional daily injections (1 ml i.v.) from 48 h after the initial bolus until day 13. Jugular and ovarian venous blood samples were taken 4-hourly over days 2–13 of the luteal phase. Blood samples were also taken at more frequent intervals (every 10–15 min for 2–3 h) to examine pulsatile secretory responses from the ovary to endogenous and gonadotrophin-releasing hormone-induced (150 ng i.m.) LH pulses on days 4, 6, 8, 10 and 12 of the luteal phase. Plasma FSH levels, ovarian steroid secretion and ovarian follicular development were measured. The ovarian follicle population was estimated daily by real time ultrasound scanning.

Immunisation against inhibin resulted in a 3- to 4-fold increase (P<0·001) in plasma FSH levels within 8 h with levels remaining elevated over controls for 6–7 days. Within 24 h of immunisation there was an increase in the number of small ovarian follicles (P<0·05) and by 3 days after treatment immunised ewes had 4–6 large ovarian follicles/ewe with this increase in the total number of large follicles being maintained for the rest of the experimental period (P<0·05). Mean ovarian oestradiol secretion during intensive bleeds was not different from controls 24 h after immunisation, but by 3 days after immunisation it was elevated 4- to 5-fold (P<0·001) over controls with this increase being maintained throughout the experiment. Similar responses to immunisation against inhibin in androstenedione secretion were observed although mean androstenedione secretion was not elevated until 7 days after treatment. In vitro antibody titres in immunised ewes remained elevated but declined steadily (P<0·001) over the experimental period.

We conclude that the initial stimulation of follicle development and ovarian steroid secretion following passive immunisation against inhibin can be attributed to increased blood FSH. However, the fact that with time FSH declined but increased follicle development was sustained, despite maintenance of high circulating antibody titres, suggests that on a longer term basis inhibin immunisation may stimulate ovarian function by interfering with the modulation of follicle development by inhibin at an ovarian level.

Journal of Endocrinology (1995) 145, 479–490
The local differential effect of prostacyclin, prostaglandin E2 and prostaglandin F2α on mammary blood flow of lactating goats
Authors: Nielsen M O , Fleet I R , Jakobsen K , Heap R B
Published: December 2008

Mammary blood flow (MBF) and milk yield are closely related in dairy ruminants, but little is known about the regulation of MBF in vivo. The local effects on MBF of injections or continuous infusions into the mammary artery of prostaglandins (PG) or indomethacin (an inhibitor of prostaglandins) respectively, were investigated in surgically prepared conscious goats. Prostacyclin (PGI2) was found to be a potent stimulator of MBF which increased linearly over the dose range 50–1000 ng. PGE2 was almost as potent as PGI2 at low doses, but tachyphylaxis occurred at doses at and above 100 ng. The response to repeated injections of PGE2 quickly declined depending on the dose. PGF2α had no effect on MBF. During infusion of indomethacin into the mammary artery MBF was reduced markedly, showing that endogenous mammary prostaglandins are involved in the regulation of vasodilatation. The results indicate that PGI2 (and to a lesser extent PGE2) has an important role in the local regulation of vascular tone in the mammary gland.

Journal of Endocrinology (1995) 145, 585–591
Insulin and IGF-I binding and tyrosine kinase activity in fish heart
Authors: Gutiérrez J , Párrizas M , Maestro M A , Navarro I , Plisetskaya E M
Published: December 2008

A study is presented of the binding of insulin and IGF-I to their respective receptors in the heart muscle of carp (Cyprinus carpio), coho salmon (Oncorhynchus kisutch), brown trout (Salmo trutta fario) and Sprague–Dawley rats. Receptor preparations were partially purified by wheat germ agglutinin affinity chromatography. Specific binding of insulin/100 mg cardiac muscle was much lower in fish (from 5·6 to 9·2%) than in rat (52·0 ± 5·0%). In both carp and trout, insulin binding to the cardiac muscle receptor preparation was significantly higher than in the white skeletal muscle (3·4 ± 0·3%, carp and 0·9 ± 0·3%, trout) or in the red skeletal muscle of carp (5·5 ± 0·8%). Specific binding of IGF-1/100 mg fish heart preparation ranged between 44 and 68%, surpassing IGF-I binding in the rat heart (20 ± 6%). The affinity of IGF-I receptors in fish heart (Kd 0·17–0·19 nm) was higher than that in rat heart (Kd 0·40 ± 0·05 nm) or insulin receptors in fish and rat heart preparations (0·25–0·72 nm). The IGF-I receptor binding was highly specific and required at least 100 nm insulin to cause any displacement of the bound ligand. Receptor tyrosine kinase activity could be stimulated in a dose-dependent manner by insulin and IGF-I, although in equimolar doses IGF-I was more potent than insulin. Maximum stimulation of tyrosine kinase activity (210–230%) in fish heart was in the same range as in other piscine tissues (150–260%) or in rat cardiac muscle (200–250%).

Journal of Endocrinology (1995) 146, 35–44
Migratory fat deposition in European quail: a role for prolactin?
Authors: Boswell T , Sharp P J , Hall M R , Goldsmith A R
Published: December 2008

The present study addresses the role of prolactin as a regulator of migratory fattening in European quail (Coturnix coturnix). Plasma prolactin levels in captive birds undergoing migratory fattening in an outdoor aviary and in the laboratory were measured by radioimmunoassay with an antibody raised against recombinant-derived chicken prolactin. No strong association between prolactin and migratory fattening was apparent, and prolactin levels were more closely related to daylength, with the highest concentrations being reached on long days. Plasma prolactin profiles were similar in intact and castrated male quail. Prolactin was secreted in a daily rhythm, with the highest concentrations occurring early in the photophase. However, when birds were food-restricted for 50 days during a migratory phase, there was no difference in fat deposition between birds food-deprived for the first half of the daily photophase compared with those deprived for the second half. Fattening was reduced in the food-restricted birds relative to ad libitum-fed controls, but there was no difference in plasma prolactin levels between the groups. Injections of ovine prolactin (4 mg/kg) significantly increased food intake and body mass of birds maintained on long days, but there were no differences in fattening between birds injected in the morning compared with those injected in the afternoon. Collectively, these results do not support a major role for prolactin in the regulation of migratory fat deposition in European quail.

Journal of Endocrinology (1995) 146, 71–79
Effect of hypothyroidism on the pituitary-gonadal axis in the adult female rat
Authors: Mattheij J A M , Swarts J J M , Lokerse P , van Kampen J T , Van der Heide D
Published: December 2008

The pituitary-ovarian axis was studied after withdrawal of thyroid hormone in 131I-radiothyroidectomized adult female rats. Oestrous cycles became prolonged and irregular within 2 weeks after the supply of thyroid hormone was stopped. If an LH surge occurred in hypothyroid rats on the day of vaginal pro-oestrus it was significantly greater in rats which had been made hypothyroid for 4–5 weeks than in controls; in hypothyroid rats with an LH surge on pro-oestrus, plasma progesterone showed a rise similar to that in controls at pro-oestrus; the ovulation rate was decreased in hypothyroid rats. About half of the rats from which blood was sampled daily in the afternoon between 7 and 18 days after tri-iodothyronine (T3) withdrawal had 1 day of pro-oestrus; on this day the LH surge was higher than in controls. On days 2 and 1 before and days 1 and 2 after this pro-oestrus, plasma progesterone was similar to that of controls on days 2 and 1 before and days 1 and 2 after pro-oestrus respectively. However, progesterone was higher in the period before and after these days. The other hypothyroid rats showed no pro-oestrus and no LH surge during this period, while their plasma progesterone levels were high on all days. On the morning of day 10 after T3 withdrawal and 5 days after the preceding pro-oestrus, most hypothyroid rats had high progesterone and low oestradiol plasma levels. In these rats, injection of gonadotrophin-releasing hormone caused a relatively small increase in LH; it did not stimulate the secretion of oestradiol or progesterone, and it did not induce ovulation. It was concluded that hypothyroidism induces major changes in the secretion of steroids by corpora lutea and growing follicles. Whether the changed steroid metabolism is the primary cause of the observed prolongation of the oestrous cycles, the increased pro-oestrous LH surge and the reduced ovulation rate remains to be investigated.

Journal of Endocrinology (1995) 146, 87–94
Effects of growth hormone antagonists on 3T3-F442A preadipocyte differentiation
Authors: Xu B C , Chen W Y , Gu T , Ridgway D , Wiehl P , Okada S , Kopchick J J
Published: December 2008

We have previously shown that a bovine (b) GH antagonist, bGH-M8, which possesses three amino acid substitutions in its third α-helix, inhibits mouse 3T3-F442A preadipocyte differentiation. In the current studies, we used the bGH and human (h) GH analogs with single amino acid substitution, bGH-G119R and hGH-G120R, for determining their biological activity using the preadipocyte differentiation assay. Short-term and long-term GH-inducible events were studied during adipose differentiation, including late marker gene expression (adipocyte protein 2), immediate early gene induction (c-fos), and tyrosine phosphorylation of intracellular proteins. The results demonstrated that these GH analogs not only failed to induce these three events, but also antagonized GH induction of c-fos expression and phosphorylation of proteins of apparent molecular mass of 95 kDa. Our present study agrees with the notion that GH must bind to the GH receptor via site one and with a second GH receptor molecule (or with some yet unidentified 'second target') through GH binding site two. This interaction is important for subsequent GH-dependent biological events.

Journal of Endocrinology (1995) 146, 131–139
Enzymatic conversion of IGF-I to des(1–3)IGF-I in rat serum and tissues: a further potential site of growth hormone regulation of IGF-I action
Authors: Yamamoto H , Murphy L J
Published: December 2008

We recently identified and characterized a protease present in rat serum which is capable of generating des(1–3)IGF-I. In this study, we have investigated the effects of GH deficiency and replacement on the activity of this protease in rat serum and tissue extracts. Protease activity was significantly higher in sera from hypophysectomized (hypox) rats than sham-operated rats (P<0·001) and GH treatment of hypox rats (human GH, 100 μg/100 g body weight i.p. for 10 days) significantly reduced the levels towards normal. The addition of IGF-I to hypox rat serum to achieve IGF-I concentrations comparable with or greater than that seen in normal rat serum had no effect on the measured protease activity. Protease activity was also detected in tissue extracts. The level of protease activity in the various tissues from sham-operated rats demonstrated the following order: liver>testes>heart> skeletal muscle>lung>thymus>kidney>brain>spleen. In all tissue extracts examined, except that from the lung, the levels of protease activity were higher in extracts from hypox rats compared with sham-operated rats. The largest differences between tissue extracts from hypox and shamoperated rats were seen in spleen (4-fold higher), kidney (2·27-fold), testes (1·55-fold) and heart (1·31-fold). In the liver, kidney and testes, GH treatment significantly reduced protease activity. Since the pattern of serum IGF-binding proteins (IGFBPs) differ in hypox rats compared with normal rats, we determined whether these changes could result in enhanced serum binding of des(1–3)IGF-I. Sera from hypox, GH-treated hypox and sham-operated rats were incubated with either 125I-IGF-I or 125I-des(1–3)IGF-I and analyzed by Sephacryl S-200 chromatography. Under the conditions used, 125I-des(1–3)IGF-I was recovered exclusively in the 7·5 kDa peak when incubated with serum from sham-operated rats. After incubation with sera from hypox or GH-treated hypox rats approximately 20% of the 125I-des(1–3)IGF-I was recovered in the 50 kDa peak with the remaining radioactivity recovered as free peptide. These observations suggest that the generation of des(1–3)IGF-I may be inversely regulated by GH and may represent yet another site of GH regulation of IGF-I action. The changes in the pattern of serum IGFBPs which occur in GH deficiency are unlikely to negate the enhanced generation of des(1–3)IGF-I by increasing binding capacity for this IGF-I variant.

Journal of Endocrinology (1995) 146, 141–148
Changes in plasma β-cell tropin concentrations during pregnancy in rats
Authors: Davenport M , Morton J L , Cawthorne M A
Published: December 2008

The mechanisms which initiate and maintain the energy partitioning into maternal tissues during pregnancy are unknown. The present study shows that in each of the weeks prior to pregnancy in the rat, plasma β-cell tropin (βCT) concentrations (nmol/l) were 0·68±0·10, 0·61 ±0·14 and 0·73±0·11 (n=11, mean±s.e.m.). During early (1-3 days) pregnancy the concentration rose to 1·32 ±0·26 and by early-mid (7–10 days) pregnancy they had increased to 1·96 ±0·41. By mid-late (14–17 days) pregnancy plasma βCT concentration had declined to the prepregnancy concentrations (0·67 ± 0·16). This mid-term increase in the circultating concentration of the lipogenic hormone βCT may contribute to the deposition of lipid associated with the early period of gestation. The increased circulating βCT could be derived from the pituitary gland neurointermediate lobe or by secretion from the placenta. It should be emphasised that the measurements in the present study represent a 'snap-shot' at discrete intervals and do not provide information about the dynamic hormonal interplay which occurs physiologically.

Journal of Endocrinology (1995) 146, 177–182
Comparison of the effects of growth hormone-releasing hormone and hexarelin, a novel growth hormone-releasing peptide-6 analog, on growth hormone secretion in humans with or without glucocorticoid excess
Authors: Giustina A , Bussi A R , Deghenghi R , Imbimbo B , Licini M , Poiesi C , Wehrenberg W B
Published: December 2008

The aim of our study was to investigate the effect of hexarelin, a novel GH-releasing peptide-6 analog, and GH-releasing hormone (GHRH) (alone or in combination) on GH secretion in adult patients with increased somatostatin tone due to chronic glucocorticoid excess. We studied seven adult patients undergoing long-term (no less than 6 months) immunosuppressive glucocorticoid treatment for non-endocrine diseases (six females and one male, age range 42–68 years) and one subject (female, age 31 years) with endogenous hypercortisolism due to adrenal adenoma. Six normal subjects (four females and two males) matched for sex and age with the patients and not undergoing any therapy served as controls. All the subjects underwent the following three tests in random order: (1) human GHRH (1–29)NH2 (100 μg in 1 ml saline) injected as an i.v. bolus at 0 min, (2) hexarelin (100 μg in 1 ml saline) injected as an i.v. bolus at 0 min and (3) hexarelin (100 μg in 1 ml of saline) plus GHRH (100 μg in 1 ml saline) injected as an i.v. bolus at 0 min. After GHRH alone the patients with glucocorticoid excess showed a blunted GH response as compared with normal subjects (median delta GH: 0·9, range 0–5·6 μg/l vs 7·1, range 0·3–14·9 μg/l). No significant differences were observed in the steroid-treated group with respect to normal subjects after hexarelin alone (median delta GH: 15·5, range 1·9–45·2 μg/l vs 17·9, range 5·5–53·9 μg/l). The GH responses after the combined stimuli were significantly decreased in the patients with glucocorticoid excess as compared with normal subjects (median delta GH: 43·5, range 21–56·9 μg/l vs 73·7, range 19·6-116·8 μg/l). The two stimuli acted in a synergistic fashion in both groups of subjects. It may be hypothesized that hexarelin influences the GH inhibitory effect of glucocorticoids in humans, acting at the hypothalamic somatostatin level.

Journal of Endocrinology (1995) 146, 227–232
Increased natriuretic peptides in fetal hearts of diabetic rats
Authors: Mulay S , Conliffe P R , Varma D R
Published: December 2008

The main purpose of these studies was to determine whether diabetic pregnancy altered maternal and fetal atrial natriuretic peptide (ANP). Diabetes was induced in rats by intravenous injection of 40 mg streptozotocin/kg on day 2 of gestation. Immunoreactive ANP in plasma, amniotic fluid and hearts on day 20 of gestation was measured by radioimmunoassay; fetal cardiac natriuretic peptides (ANP, proANP and BNP) were separated by reverse-phase high pressure liquid chromatography. Diabetes caused an increase in fetal plasma insulin, placental weight, amniotic fluid volume, the ratio of the fetal heart to body weight, maternal and fetal plasma ANP, fetal cardiac ANP and fetal cardiac BNP. It is suggested that the maternal diabetes-induced increase in fetal ANP might be related to fetal myocardial hypertrophy and could contribute to hydramnios.

Journal of Endocrinology (1995) 146, 255–259
Analysis of epidermal growth factor action in human myometrial smooth muscle cells
Authors: Környei J L , Li X , Lei Z M , Rao Ch V
Published: December 2008

The present study investigated the mechanisms involved in the mitogenic action of epidermal growth factor (EGF) in cultured human myometrial smooth muscle cells. The cells contained EGF/transforming growth factor-α (TGF-α) receptors as well as EGF and TGF-α mRNA transcripts and the corresponding proteins. Culturing with human EGF resulted in concentration- and time-dependent increases in cell density. The maximal increase was seen at 1 nm followed by a decrease to control levels at 100 nm EGF. The EGF increased cell density from 4 to 8 days followed by a plateau coinciding with the cells reaching confluence. EGF treatment concomitantly decreased the average size of cells. TGF-α mimicked EGF and there was no synergism between the two, suggesting a common mechanism of action. Although the presence of 10% fetal bovine serum enhanced overall cell growth, it was not required for EGF and TGF-α action. The receptor antibody, which is directed against the extracellular domain and can inhibit ligand binding to the receptors, dramatically inhibited the basal cell growth and exogenous EGF reversed the antibody effect. While TGF-α antibody was only marginally effective, EGF antibody had no effect on basal cell growth. Lavendustin (a tyrosine kinase inhibitor), calphostin (a protein kinase C inhibitor), but not H-89 (a protein kinase A inhibitor), inhibited EGF action. Indomethacin, a cyclo-oxygenase inhibitor, completely inhibited, whereas nordihydroguaiaretic acid, a lipoxygenase inhibitor, slightly inhibited EGF action. While estradiol-17β modestly inhibited basal as well as EGF-stimulated myometrial smooth muscle cell density, progesterone had no effect.

In summary, mitogenic action of EGF in human myometrial smooth muscle cells does not require serum components and it involves tyrosine kinase and protein kinase C signaling and eicosanoids from the cyclo-oxygenase pathway of arachidonic acid metabolism.

Journal of Endocrinology (1995) 146, 261–270
Interleukin-1 and tumor necrosis factor-α increase insulin-like growth factor-binding protein-3 (IGFBP-3) production and IGFBP-3 protease activity in human articular chondrocytes
Authors: Olney R C , Wilson D M , Mohtai M , Fielder P J , Smith R L
Published: December 2008

IGF-I is the major anabolic factor for cartilage matrix production. Chondrocytes and cartilage treated with interleukin-1α (IL-1α), and chondrocytes from several models of inflammatory joint disease, exhibit reduced responsiveness to IGF-I. Since the IGF-binding proteins (IGFBPs) modulate the effects of IGF-I, we examined the effect of IL-1α and tumor necrosis factor-α (TNF-α) on IGFBP production by normal human articular chondrocytes in primary culture. Western ligand blots and immunoprecipitation of conditioned medium samples showed that articular chondrocytes produced IGFBPs-2, −3 and −4 and glycosylated IGFBP-4. Both IL-1α and TNF-α increased chondrocyte production of IGFBP-3, but did not alter IGFBP-4 production. The activity of a neutral metalloprotease with the ability to cleave IGFBP-3 was also increased by IL-1α. These data suggest that the cytokines IL-1α and TNF-α may act to reduce IGF-I access to chondrocytes by increasing production of IGFBP-3. This may be a factor in the decreased matrix production in the inflammatory arthritides.

Journal of Endocrinology (1995) 146, 279–286
Changes in calmodulin concentration and cyclic 3′,5′-nucleotide phosphodiesterase activity in skeletal muscle of hyper- and hypothyroid rats
Authors: Mano T , Iwase K , Yoshimochi I , Sawai Y , Oda N , Nishida Y , Mokuno T , Kotake M , Nakai A , Hayakawa N , Kato R , Nagasaka A , Hidaka H
Published: December 2008

Hyper- and hypothyroid states occasionally induce skeletal muscle dysfunction i.e. periodic paralysis and thyroid myopathy. The etiology of these diseases remains unclear, but several findings suggest that the catecholamine-β-receptor-cAMP system or other messenger systems are disturbed in these diseases. In this context, we evaluated changes in the cyclic 3′,5′-nucleotide metabolic enzyme, cyclic 3′,5′-nucleotide phosphodiesterase (PDE) and calmodulin concentrations in skeletal muscles of hyper- and hypothyroid rats.

Activities of cyclic AMP-PDE were low in skeletal muscle both from hyper- and hypothyroid rats, and calmodulin concentration was high in hyperthyroid and low in hypothyroid rats, as compared with normal rats. DE-52 column chromatographic analysis showed that the cGMP hydrolytic activity in peak I and the cAMP hydrolytic activity in peak II were decreased in hypothyroid rats, whereas cAMP hydrolytic activity in peak III was unchanged. The cAMP hydrolytic activity in peak III was decreased in hyperthyroid rats, but the activities in peaks I and II were unchanged. These findings indicate that cAMP and calmodulin may have some role in skeletal muscle function in the hyperthyroid state, and that cAMP and calmodulin-dependent metabolism may be suppressed in the hypothyroid state.

Journal of Endocrinology (1995) 146, 287–292
Inhibin and oestradiol-17β in antral follicles of various size classes of cyclic rats
Authors: van Cappellen W A , van Leeuwen E C M , Meijs-Roelofs H M A , Kramer P , Sander H J , de Jong F H
Published: December 2008

On the various days of the 5-day oestrous cycle of the rat, ovarian antral follicles were dissected out and grouped in five size classes. Four follicles of the same size class were homogenized jointly in medium, after which inhibin-like bioactivity, inhibin immunoreactivity and oestradiol-17β content were measured. In general, there was a significant correlation between immunologically and biologically active inhibin levels in the different size classes; overall correlation was 0·85 (n=87, P<0·00001). In the smallest antral follicles (classes 1 and 2) inhibin bioactivity was detected only during the first three days of the cycle. With increasing follicle size, inhibin bioactivity and immunoreactivity increased, with maximal activity present in the largest, i.e. preovulatory, follicles (class 5) during the last three days of the cycle (the day of oestrus denotes day 1 of the cycle). These results indicate that only follicles which reach the antral stage at oestrus, and are known to be recruited by the periovulatory FSH peak, acquire the potency to produce biologically active inhibin. This is the cohort of follicles from which selection of ovulatory follicles will normally take place.

In contrast to inhibin, follicular oestradiol-17β concentrations were negligible until the last days of the cycle when oestradiol-17β was present in follicles larger than class 2; levels increased with increasing follicle size and a maximal level was found in preovulatory follicles at pro-oestrus.

It is concluded that (1) there is a good correlation between follicular content of inhibin-like bioactivity and inhibin immunoreactivity and (2) there are differences between patterns of follicular levels of inhibin immunoreactivity and oestradiol-17β during the ovarian cycle: follicles destined to ovulate start to produce inhibin in volume classes 1 and 2 and only thereafter also contain oestradiol-17β. Follicles entering classes 1 and 2 at dioestrus-2 and -3 or at pro-oestrus do not produce inhibin and become atretic.

Journal of Endocrinology (1995) 146, 323–330
Ovulation rate and the concentrations of gonadotrophins and metabolic hormones in ewes infused with glucose during the late luteal phase of the oestrous cycle
Authors: Downing J A , Joss J , Scaramuzzi R J
Published: December 2008

The positive relationship between nutrition and ovulation rate was investigated in sheep infused intravenously with glucose. Ovulation rate increased (2·0±0·0 vs 2·4 ± 0·3) when ewes were given an infusion of glucose (60–65 mm/h) for five days in the late luteal phase of the oestrous cycle. The effect of glucose was obtained without any significant change in LH secretion. The concentration of FSH in glucose-infused ewes was lower during the infusion (luteal phase) but higher during the early follicular phase. These data suggest that the change in ovulation rate occurred without increased gonadotrophin support to the follicle during the late luteal phase, which is the period of the sheep oestrous cycle during which improved nutrition increases ovulation rate. There were no changes in GH or prolactin, but changes in circulating glucose and insulin levels were detected. We conclude that insulin, because of its role in cell growth and metabolism, is involved in mediating ovulation responses to nutritional stimuli, either directly or more likely by the stimulation of insulin-mediated glucose uptake.

Journal of Endocrinology (1995) 146, 403–410
In vitro regulation of rat Sertoli cell inhibin messenger RNA levels by transforming growth factor-β1 and tumour necrosis factor α
Authors: Le Magueresse-Battistoni B , Morera A M , Benahmed M
Published: December 2008

In the present study, we examined the in vitro regulation of 20-day-old rat Sertoli cell inhibin α- and βB-subunits mRNA levels by transforming growth factor-β1 (TGF-β1) and tumour necrosis factor α (TNFα), two factors produced in the testis. Addition of TGF-β1 to highly purified cultured Sertoli cells resulted in a time- and dose-dependent enhancement in the α-subunit mRNA levels (ED50=2·4 pm; maximal increase of 2·6-fold after 48 h of treatment), without affecting the βB-subunit mRNA levels. Similarly, activin A up-regulated the α-but did not modulate the βB-subunit mRNA levels. By contrast, TNFα decreased in a time- and dose-dependent fashion the mRNA levels of the two inhibin subunits α and βB (IC50=29 pm for both subunits; maximal decrease of 4·4- and of 4-fold after 72 and 24 h of treatment for respectively the α- and βB-subunits). The effects of TGF-β1 and TNFα on inhibin mRNA levels occurred within a dose range that might be expected under physiological conditions. In addition, TGF-β1-treated Sertoli cells responded to FSH or dibutyryl cyclic AMP ((Bu)2cAMP) by a further and significant additive increase of the α-subunit mRNA levels. TNFα-treated Sertoli cells responded significantly to FSH and to (Bu)2cAMP, thus attenuating the inhibitory action of TNFα on the α-inhibin mRNA levels. Together, the present findings emphasize the ability of some local growth factors to modulate the effects of FSH on Sertoli cell function.

Journal of Endocrinology (1995) 146, 501–508
Similarities between hamster pancreatic islet beta (HIT) cell vasopressin receptors and V1b receptors
Authors: Richardson S B , Laya T , VanOoy M
Published: December 2008

Vasopressin (VP) elicits almost identical insulin-stimulatory dose responses in isolated mouse islets and hamster β (HIT) cells. We have further pharmacologically characterized HIT cell VP receptors by comparing the potencies of a series of VP agonists including the novel V1b agonist, desamino(d-3-(3′-pyridyl)-Ala2,Arg8)VP (d(d-3-Pal)VP), in stimulating insulin secretion and inositol phosphate (IP) production. The relative orders of potency of VP analogues were parallel in both respects: desamino-Arg-VP (dAVP)>Arg-vasotocin (AVT)= VP>oxytocin (OXY)>desamino-d-Arg-VP (ddAVP)> d(d-3-Pal)VP. dAVP, the most potent agonist tested, behaved as a V1 but non-V1a agonist. The potency of d(d-3-Pal)VP relative to VP was 1:134 in stimulating insulin secretion and 1:40 with respect to IP production. In HIT cell monolayers, the relative order of affinity of analogues in competition for binding with [3 H]AVP was: dAVP>AVT=VP>V1a antagonist>OXY>ddAVP>V2 antagonist=d(d-3-Pal)VP, in parallel with their biological activity. The relative orders of potency and affinity parallel those reported for corticotrophic V1b receptors. Binding studies with hamster liver membranes indicate that the hepatic VP receptor belongs to the V1a class. We conclude that VP activates phospholipase C and interacts with functional VP receptors of the V1 type, which do not belong to the V1a subclass and which are similar to V1b receptors.

Journal of Endocrinology (1995) 147, 59–65
Synergism of GH and IGF-I in stimulation of sulphate uptake by teleostean branchial cartilage in vitro
Authors: Cheng C M , Chen T T
Published: December 2008

The combined effects of teleostean GH and human IGF-I in the regulation of teleost branchial cartilage growth were examined. Ceratobranchial cartilages were dissected from the common carp (Cyprinus carpio) and maintained in a defined culture medium supplemented with recombinant striped bass GH (sbGH), human IGF-I (hIGF-I) or both, and the uptake of [35S]sulphate by cartilage explants was measured. sbGH alone in the culture medium did not exhibit a significant stimulatory effect on the uptake of [35S]sulphate when compared with the controls. However, with hIGF-I in the culture medium, as low as 1 ng/ml, the stimulatory effect of sbGH was apparent and dose-dependent. The synergism of sbGH and hIGF-I was observed at the concentrations of 1 and 10 ng IGF/I/ml tested. At a constant hIGF-I concentration (10 ng/ml), a maximum stimulatory effect was detected with 3 μg recombinant sbGH/ml, at which point a 2·3-fold increase in sulphation activity was obtained when compared with the treatment with hIGF-I alone. A similar dose-dependent stimulatory effect was observed when native common carp and bonito GHs were tested using this assay system. These results suggest that the synergistic effect of sbGH and hIGF-I on sulphation activity is a common biological function of teleost GH, thus ruling out the possibility of experimental artifacts resulting from utilization of heterologous GH. Furthermore, experiments were conducted to test whether the synergism between sbGH and hIGF-I occurred between sbGH and insulin. Results showed that although bovine insulin was less effective than hIGF-I on the stimulation of [35S]sulphate uptake, the synergistic effects of sbGH with hIGF-I and sbGH with insulin were similar at the concentrations tested. The concept of a 'dual effector' mechanism for GH action in teleosts is supported by these findings.

Journal of Endocrinology (1995) 147, 67–73