bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the gonadotrophin-releasing hormone receptor in αT3-1 pituitary gonadotroph cells
Authors: Anderson L. , Milligan G. , Eidne K. A. 
Published: December 2008

ABSTRACT
The present study has characterized the gonadotrophin-releasing hormone (GnRH) receptor in immortalized αT3-1 pituitary gonadotroph cells. GnRH and GnRH analogues produced both a dose- and time-dependent increase in total inositol phosphate (IP) accumulation. The rank order of potency of these analogues was the same as that obtained in parallel receptor-binding studies in αT3-1 cells. These responses were abolished following pretreatment with a GnRH antagonist. The use of a specific inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) assay demonstrated a rapid but short-lived rise in Ins(1,4,5)P3 production. Intracellular calcium ([Ca2+]i) was subsequently measured in αT3-1 cells using dual wavelength fluorescence microscopy combined with dynamic video imaging. GnRH produced a biphasic rise in [Ca2+]i. The initial calcium transient was complete within seconds while the smaller secondary plateau phase lasted several minutes. G-protein involvement in the IP response to GnRH in αT3-1 cells was investigated using sodium fluoride (NaF) and pertussis toxin (PTx) which activate and inactivate G-proteins respectively. Like GnRH, NaF produced a dose- and time-dependent increase in IP accumulation. Activation of phospholipase C in these cells by either GnRH or NaF was PTx-insensitive, suggesting that the G-protein involved was neither Gi nor Go but more probably Gq. Immunoblot analysis of αT3-1 cell membranes using antisera raised against the predicted C-terminal decapeptide of the α subunit of Gq demonstrated the presence of Gq in αT3-1 cells. Collectively these results show that the GnRH receptors expressed in αT3-1 cells are coupled to the phosphatidylinositol second messenger pathway via a specific G-protein. αT3-1 therefore represents a convenient model in which to study GnRH-related second messenger pathways.
Journal of Endocrinology (1993) 136, 51–58
Induction of ornithine decarboxylase immunoreactivity in the male mouse kidney following testosterone treatment: an axial heterogeneity in the proximal tubule
Authors: Koibuchi N. , Matsuzaki S. , Ma H.-T. , Sakai M. , Yamaoka S. 
Published: December 2008

ABSTRACT
The effect of testosterone on the activity of ornithine decarboxylase (ODC), its protein level and immunocytochemical distribution were examined in the mouse kidney. Male BALB C mice at 8 weeks of age were used throughout. Fourteen hours before death, they received a subcutaneous injection of testosterone (1 mg/animal) or solvent to measure renal ODC activity or to detect the distribution of ODC immunoreactivity in the kidney. Renal ODC activity and the content of the enzyme were markedly increased after testosterone treatment. Histologically, few cells that were obviously immunoreactive to ODC were observed in the control animals and in the testosterone-treated animals a marked increase in ODC immunoreactivity was observed only in the cortex. ODC immunoreactive cells were located diffusely in the proximal tubule. In the pars recta, cells were stained weakly and homogeneously, while in the pars convoluta, the luminal surface of the cells showed stronger immunoreactivity. Moreover, many granule-like particles that were strongly ODC immunoreactive were observed inside the lumen of the pars convoluta. These results show that testosterone treatment induces an increase in ODC content in certain cells located in the proximal tubule of the cortex.
Journal of Endocrinology (1993) 136, 85–89
Growth hormone deficiency in 'little' mice results in aberrant body composition, reduced insulin-like growth factor-I and insulin-like growth factor-binding protein-3 (IGFBP-3), but does not affect IGFBP-2, -1 or -4
Authors: Donahue L. R. , Beamer W. G. 
Published: December 2008

ABSTRACT
Although GH is known to regulate somatic growth during development, its role in regulating adult body composition is less well defined. The effects of GH on individual body compartments – water, fat, protein and mineral – are achieved both by the action of GH and by a GH-induced hormone, insulin-like growth factor-I (IGF-I). We used a genetic model of GH deficiency, the 'little' (gene symbol lit) mouse, to determine the GH regulation of IGF-I and its insulin-like growth factor-binding proteins (IGFBPs) and to define the interaction between these hormones and each body compartment in adults.
Our results showed that GH-deficient lit/lit mice had reduced levels of serum IGF-I (range 38–130 μg/l) compared with normal lit/+ littermates (range 432–567 μg/l) between 2 and 52 weeks of age. The lit/lit mice did not experience the fivefold increase in IGF-I between 2 and 4 weeks of age that was seen in lit/+ mice. In lit/lit serum, overall binding of 125I-labelled IGF-I to the four IGFBPs was reduced, solely in response to a reduced amount of IGFBP-3. No overall differences were found between lit/lit and lit/+ mice in the binding of 125I-labelled IGF-I to IGFBP-2, -1 or -4. Age-related declines in IGF-I and IGFBPs were seen in lit/lit mice. However, adult levels of IGF-I were maintained in lit/+ mice to at least 52 weeks of age, as were levels of IGFBP-1 and -4, while IGFBP-3 and -2 declined with age.
With respect to body composition, comparison of lit/lit with lit/+ mice showed that the lit/lit mice were characterized by abnormally large adipose tissue stores and reduced body water, protein and mineral from 2 weeks onward. These changes occurred despite normal energy intake in lit/lit mice up to 52 weeks of age, indicating that neither undernutrition nor hyperphagia is characteristic of this GH-induced model of obesity. Furthermore, lit/lit males accrued more body fat beginning at an earlier age than lit/lit females. With advancing age, the per cent body fat increased in both lit/lit and lit/+ mice, while the per cent body water and mineral declined. In lit/lit but not lit/+ mice, per cent protein also declined with age. The changes in body water and fat are attributable to lack of adequate GH in the genetically GH-deficient lit/lit mouse. On the other hand, the changes in body protein are more likely to be effects of IGF-I. Changes in mineral observed in lit/lit mice could be the result of action by GH, IGF-I or both hormones. Therefore, when GH is chronically manipulated by GH deficiency as in lit/lit mice, by GH excess as in acromegaly, or by GH therapy, all four body compartments are affected, suggesting that GH therapy is most valuable when the treatment goal is to alter overall body composition.
Journal of Endocrinology (1993) 136, 91–104
Oestradiol-17β modulates the actions of pharmacologically distinct forms of protein kinase C in rat anterior pituitary cells
Authors: Thomson F. J. , Johnson M. S. , MacEwan D. J. , Mitchell R. 
Published: December 2008

ABSTRACT
Phorbol ester-induced release of LH and GH from rat anterior pituitary tissue in vitro is differentially inhibited by some, but not other, inhibitors of protein kinase C (PKC), suggesting that pharmacologically distinct species of PKC may have different functional roles in these cells. Since stimulus-induced anterior pituitary hormone release can be enhanced by oestradiol-17β (OE2) pretreatment, we investigated the effect of OE2 treatment of long-term (4 weeks) ovariectomized rats on the amount, activity and cellular actions of pharmacologically distinct PKC species in rat anterior pituitary tissue. Here we report that OE2 treatment enhanced phorbol 12,13-dibutyrate (PDBu)-induced LH but not GH release measured in vitro. This effect of OE2 on LH release may involve synthesis of additional PKCs that are not targeted by the synthetic diacylglycerol, 1,2-dioctanoyl-snglycerol (DOG). Measurements of anterior pituitary PKC activity and [3H] phorbol ester-binding studies suggested that the facilitatory action of OE2 on LH release may occur, at least in part, by altering the quantity and activity of PKC(s). Our results also demonstrate that the OE2-induced PKC(s) which facilitate LH release may be of the type that are not dependent upon raised intracellular Ca2+ for their activation and display distinct pharmacological properties (being readily activated by PDBu, but not by DOG, and are staurosporine-sensitive but H7-insensitive). This facilitatory action of OE2 on PKC-induced LH release does not appear to involve OE2-induced changes in the affinity of existing PKC(s) for PDBu, or changes in the amount of releasable LH in the pituitary prior to the stimulus.
Journal of Endocrinology (1993) 136, 105–117
Bradykinin and vasopressin activate phospholipase D in rat Leydig cells by a protein kinase C-dependent mechanism
Authors: Vinggaard A. M. , Hansen H. S. 
Published: December 2008

ABSTRACT
In the present study we report that bradykinin stimulated phospholipase D activity in rat Leydig cells. Bradykinin added for 8 min stimulated choline formation in a dose-dependent manner and, in the presence of ethanol, bradykinin (100 nmol/l) stimulated transphosphatidylation by phospholipase D resulting in the formation of phosphatidylethanol. This stimulation was abolished after down-regulation of protein kinase C by long-term pretreatment for 22 h with phorbol 12-myristate 13-acetate (PMA). The stimulation of phospholipase D by the simultaneous addition for 8 min of maximum concentrations of PMA and vasopressin (AVP), PMA and bradykinin, or AVP and bradykinin produced no additive phosphatidylethanol or choline response, suggesting that AVP, bradykinin and PMA stimulated phospholipase D-catalysed phosphatidylcholine hydrolysis by a similar protein kinase C-dependent mechanism. Furthermore, LH (10 ng/ml), insulin (500 nmol/l), GH (100 ng/ml), interleukin-1β (5 U/ml) and platelet-activating factor (200 nmol/l) were found not to activate phospholipase D, whereas the Ca2+ ionophore A23187 (10 μmol/l) stimulated phosphatidylethanol formation, suggesting that Ca2+ might be a regulator of phospholipase D in Leydig cells.
Journal of Endocrinology (1993) 136, 119–126
Growth hormone (GH) suppression of catecholamine turnover in the chicken hypothalamus: implications for GH autoregulation
Authors: Lea R. W. , Harvey S. 
Published: December 2008

ABSTRACT
GH administered centrally or peripherally inhibits basal or secretagogue-induced GH secretion in domestic fowl. Since the release of pituitary GH is neurally regulated by the hypothalamus, GH autoregulation may be mediated by changes in the content or metabolism of hypothalamic monoamines. When chicken GH (500 μg/kg body weight) was injected i.v. into laying hens, tissue catecholamine (adrenaline, noradrenaline and dopamine) concentrations in the preoptic area (POA) and medial basal hypothalamus (MBH) were depleted for 2–24 h, as were concentrations of dihydroxyphenylacetic acid, a dopamine metabolite. The serotonin (5-HT) content of the POA and MBH was unaffected by i.v. GH administration, although a reduction in MBH 5-hydroxyindoleacetic acid suggested a tissue-specific inhibition of 5-HT turnover. Qualitatively similar results were observed in laying hens 24 h after the intracerebroventricular injection of chicken GH (10 μg/bird). These results therefore demonstrate aminergic actions of GH within the chicken hypothalamus which may mediate GH autoregulation. However, as amine metabolism is not only suppressed when endogenous GH secretion is reduced, but also at times when normal GH secretion is restored, these aminergic effects may also reflect other actions of GH on central function.
Journal of Endocrinology (1993) 136, 245–251
Acute or chronic immunoneutralization of somatostatin does not affect growth hormone or thyroid hormone secretion in sheep
Authors: Van Kessel A. G. , Laarveld B. 
Published: December 2008

ABSTRACT
The effect of acute or chronic immunoneutralization of somatostatin (SRIF) on plasma GH, thyrotrophin (TSH) and thyroid hormones was examined. Acute responses to SRIF immunoneutralization were examined using 30 intact male lambs (19·8 ±0·6 kg) assigned to one of five treatment groups such that control (C) lambs received no anti-SRIF immunoglobulin and SRIF-immunized (SI) lambs received 2 mg (SI2), 10 mg (SI10), 20 mg (SI20) or 100 mg (SI100) anti-SRIF immunoglobulin/kg body weight (BW). Control immunoglobulin was administered such that all lambs received 100 mg total immunoglobulin protein/kg BW. Effects of chronic SRIF immunoneutralization were examined using C and SI100 lambs which received additional (40 mg/kg BW) control and anti-SRIF immunoglobulin respectively, 4 and 8 days following the initial dose. Blood samples were collected from all lambs, at 10-min intervals, for 5 h immediately following initial immunoglobulin infusion and, from C and SI100 lambs, at 10-min intervals, for 5 h at 11 days following initial immunoglobulin infusion. At the end of each 5-h sampling period, pituitary and thyroid function was examined by i.v. challenge with thyrotrophin-releasing hormone (TRH; 0·33 μg/kg BW). Basal plasma GH and thyroxine (T4) and the GH, TSH, T4 and tri-iodothyronine (T3) responses to TRH were not influenced by acute or chronic immunoneutralization of SRIF. Acute, but not chronic, immunoneutralization of SRIF elevated basal plasma T3 in SI100 lambs only. The results suggest that SRIF, under physiological conditions, does not influence GH or thyroid hormone secretion in sheep but may influence thyroid hormone metabolism acutely.
Journal of Endocrinology (1993) 136, 261–269
The role of thyroidal type-I iodothyronine deiodinase in tri-iodothyronine production by human and sheep thyrocytes in primary culture
Authors: Beech S. G. , Walker S. W. , Dorrance A. M. , Arthur J. R. , Nicol F. , Lee D. , Beckett G. J. 
Published: December 2008

ABSTRACT
We have studied the origin of tri-iodothyronine (T3) secreted by human and sheep thyrocytes in primary culture and also the expression of type-I thyroidal iodothyronine deiodinase (ID-I) in the thyroid and liver of man and various other animals. Inhibitors of ID-I reduced T3 secretion from human but not sheep thyrocytes. In contrast, inhibitors of de-novo thyroid hormone synthesis reduced both thyroxine (T4) and T3 production in sheep thyrocytes, but had no effect on the T3 secreted by human thyrocytes. Human thyrocytes did not produce T4 under the culture conditions used, although some endogenous T4 was present in the cells following their isolation. Although thyrotrophin (TSH) stimulated T3 production in both human and sheep thyrocytes, iodine in the form of potassium iodide was only essential for T3 and T4 production by the sheep cells. Although 125I from Na125I was incorporated into T3 and T4 in TSH-stimulated sheep thyrocytes, no 125I incorporation into T3 or T4 was detected in TSH-stimulated human thyrocytes. Using activity measurements and affinity labelling, ID-I was present in the livers of all species studied, but ID-I could not be detected in thyroid tissue from cattle, pigs, sheep, goats, rabbits, deer or llamas. In contrast, thyroid tissue from man, mice, guinea-pigs and rats had significant ID-I activity and expressed an affinity-labelled protein with a molecular mass of approximately 28·1 kDa on SDS-PAGE.
These data show that under the culture conditions used, sheep thyrocytes produced T3 by de-novo synthesis, whilst human thyrocytes produced T3 by deiodination of endogenous T4. We conclude that thyroidal ID-I shows marked species difference in its expression and that, in those species which express the enzyme (man, mice, guinea-pigs and rats, in this study), it appears that it may make an important contribution to thyroidal T3 production.
Journal of Endocrinology (1993) 136, 361–370
Effect of selective serotonin agonists on basal, corticotrophin-releasing hormone- and vasopressin-induced ACTH release in vitro from rat pituitary cells
Authors: Calogero A. E. , Bagdy G. , Moncada M. L. , D'Agata R. 
Published: December 2008

ABSTRACT
The present study was undertaken to evaluate the serotonin (5-HT) receptor subtype(s) by which 5-HT acts on the pituitary to stimulate ACTH secretion. We tested the effects of the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), the 5-HT1C receptor agonist metachloro-phenylpiperazine (m-CPP), which also binds to other 5-HT receptors with lower affinity, and the 5-HT2/1C receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) on basal, corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP)-stimulated ACTH release from primary rat anterior pituitary cell cultures. 5-HT, 8-OH-DPAT and DOI significantly increased basal ACTH release, an effect which was antagonized by 5-HT receptor antagonists. 5-HT and DOI were effective at nanomolar concentrations whereas 8-OH-DPAT was effective at higher concentrations. 5-HT, 8-OH-DPAT (both at 10 nmol/l) and DOI (at higher concentrations) blunted the stimulatory effect of CRH. The suppressive effects of 8-OH-DPAT and DOI on CRH-stimulated ACTH release were antagonized by (−)propranolol, a β-adrenergic receptor antagonist which binds the 5-HT1A receptor with elevated affinity, and ketanserin, a 5-HT2 receptor antagonist respectively. 5-HT, 8-OH-DPAT and DOI showed additive stimulatory effects with AVP but only at the highest concentration tested, whereas m-CPP potentiated AVP-induced ACTH release at concentrations of 1 nmol/l or more. This effect was antagonized by metergoline, a non-selective 5-HT receptor antagonist and mianserin, an antagonist which binds the 5-HT1C receptor with elevated affinity.
Thus (1) 5-HT and selective 5-HT agonists such as 8-OH-DPAT, m-CPP and DOI modulate ACTH release by acting directly at the pituitary level; (2) serotonergic stimulation of basal ACTH release is mediated by both 5-HT2 and 5-HT1A receptors; (3) serotonergic inhibition of CRH-stimulated ACTH release is mediated by 5-HT1A and 5-HT2 receptors; whereas (4) serotonergic potentiation of AVP-stimulated ACTH release is mediated mainly by 5-HT1C receptors.
Journal of Endocrinology (1993) 136, 381–387
Liposome-mediated macrophage depletion: an experimental approach to study the role of testicular macrophages in the rat
Authors: Bergh A. , Damber J.-E. , van Rooijen N. 
Published: December 2008

ABSTRACT
Liposome-entrapped dichloromethylene diphosphonate was injected locally into the right testes of adult rats. This treatment, which has been found to deplete resident macrophages in some other organs, reduced the number of testicular macrophages by at least 90%. Testicular weight and seminiferous tubule morphology were unaffected by liposome treatment. Leydig cell testosterone secretion gradually declined in the macrophage-depleted testes, and there was a compensatory increase in Leydig cell size and testosterone secretion in the contralateral saline-injected testes. These observations suggest that macrophages influence Leydig cell function locally. It is concluded that liposome-mediated depletion of testicular macrophages may serve as an experimental model with which to study the physiological role of these cells.
Journal of Endocrinology (1993) 136, 407–413
Effect of dopamine on adenylate cyclase activity, polyphosphoinositide metabolism and cytosolic calcium concentrations in frog pituitary melanotrophs
Authors: Desrues L. , Lamacz M. , Jenks B. G. , Vaudry H. , Tonon M. C. 
Published: December 2008

ABSTRACT
It has previously been shown that dopamine plays a pivotal role in the regulation of α-melanocyte-stimulating hormone (α-MSH) secretion from the intermediate lobe of the pituitary. In the present study, we have investigated the various intracellular mechanisms that are associated with the action of dopamine on frog pituitary melanotrophs. Dopamine reduced forskolin-stimulated cyclic adenosine monophosphate (cAMP) production and the inhibitory effect of dopamine was blocked by the dopaminergic D2 receptor antagonist sulpiride. The D2 receptor agonist apomorphine inhibited incorporation of [3H]inositol into membrane phospholipids. Dopamine also inhibited the formation of inositol trisphosphate and provoked accumulation of phosphatidylinositol bisphosphate. The inhibitory effect of dopamine on inositol trisphosphate production was mimicked by D2 receptor agonists and blocked by sulpiride. Using a double-wavelength microfluorimetric approach, we found that dopamine caused a rapid and transient decrease in K+-evoked stimulation of intracellular calcium concentration. The timecourses of the responses of the various intracellular messengers indicate that blockage of voltagedependent calcium channels is the primary event associated with activation of dopamine D2 receptors, while inhibition of polyphosphoinositide breakdown, related to blockage of voltage-dependent calcium channels, and reduction of cAMP production are secondary events which may contribute to the sustained inhibitory effect of dopamine on α-MSH release.
Journal of Endocrinology (1993) 136, 421–429
Pregnancy in growth hormone-deficient rats: assessment of insulin-like growth factors (IGFs), IGF-binding proteins (IGFBPs) and IGFBP protease activity
Authors: Gargosky S. E. , Nanto-Salonen K. , Tapanainen P. , Rosenfeld R. G. 
Published: December 2008

ABSTRACT
Pregnancy in rodents is associated with important maternal metabolic changes. Early pregnancy is considered to be an anabolic phase of nutrient storing, while in late pregnancy, a catabolic phase develops to help meet the metabolic demands of the rapidly growing conceptus. Similarly, major changes also occur in the IGFs, IGF-binding proteins (IGFBPs) and GH axis. In the rat, maternal serum IGF-I levels increase from early to mid-pregnancy, after which IGF-I levels decline. Conversely, as IGF-I levels decline, pituitary-derived rat GH increases twofold. This coincides with a decrease in IGFBP-3 and the appearance of an IGFBP protease. However, the physiological role of these changes is unclear.
The aim of our study was to examine the roles of GH, IGFs and IGFBPs during pregnancy in a unique isolated GH-deficient rat model, spontaneous dwarf rats.
Pregnancy in GH-deficient dams resulted in a significantly reduced litter number, and maternal weight gain (day 21–day 1) was reduced by 28% when compared with dams with normal GH levels (GH-normal dams). In the sera of GH-normal dams, IGF-I levels increased 2·6-fold by day 4 of pregnancy and then progressively declined to below non-pregnant levels. Serum IGF-II levels were low and remained unchanged. Western-ligand blot analysis showed that IGFBP-3 was present in non-pregnancy and early pregnancy sera, but declined dramatically after day 12. This decline in IGFBP-3 coincided with the detection of an IGFBP protease. In contrast, in non-pregnancy sera from GH-deficient rats, serum IGF-I concentrations were 10% of the levels seen in GH-normal females, and neither IGF-I nor IGF-II concentrations changed with pregnancy. Furthermore, in GH-deficient dams, serum IGFBP-3 (as assessed by Western-ligand blot analysis) was low in non-pregnancy and early pregnancy sera, and became undetectable by day 12 of pregnancy. The low concentrations of IGFBP-3 in early pregnancy serum from GH-deficient rats coincided with IGFBP-proteolytic activity, and the decline in serum IGFBP-3 after day 16 was the result of increased protease activity.
In conclusion, isolated GH deficiency results in: (1) reduced maternal weight gain and correspondingly smaller litter sizes; (2) low and unchanged maternal serum IGF-I levels; (3) low, but declining, serum IGFBP-3 levels; and (4) activity of IGFBP protease(s) detectable in early and late pregnancy, which may modulate the bioavailability and bioactivity of IGFs by regulating IGFBP-3.
Journal of Endocrinology (1993) 136, 479–489