Search Results
Search for other papers by L.A. SALAKO in
Google Scholar
PubMed
Search for other papers by A. J. SMITH in
Google Scholar
PubMed
Search for other papers by R. N. SMITH in
Google Scholar
PubMed
SUMMARY
Extracts of porcine thyroid containing calcitonin produced increases in urinary flow and urinary electrolyte content when infused or injected into anaesthetized rabbits. This response occurred more rapidly after intraaortic than after intravenous injection and was accompanied by an increase in glomerular filtration rate (inulin clearance) and renal plasma flow (paraaminohippuric acid clearance).
Preparations of calcitonin failed to affect the short-circuit current in isolated frog skin.
Although an effect of calcitonin on renal tubular transport mechanisms cannot be excluded it seems likely that one mechanism responsible for the diuretic effect of this compound in the rabbit is an increase in renal blood flow.
Search for other papers by K. Rajkumar in
Google Scholar
PubMed
Search for other papers by D. E. Kerr in
Google Scholar
PubMed
Search for other papers by R. N. Kirkwood in
Google Scholar
PubMed
Search for other papers by B. Laarveld in
Google Scholar
PubMed
ABSTRACT
Somatostatin-14 (SRIF-14) inhibited, in a concentration-dependent manner, LH- and forskolin-stimulated cyclic adenosine monophosphate (cAMP) induction in porcine granulosa and luteal cells. The inhibitory effect of SRIF-14 on hormone-induced cAMP generation was more potent in porcine ovarian cells than in the GH-3 pituitary cell line. The inhibitory effect of SRIF-14 was impeded by neutralizing its biological activity with specific antiserum. Preincubation of luteal and granulosa cells with phorbol 12-myristate 13-acetate (PMA) enhanced LH- and forskolin-stimulated cAMP levels. SRIF-14 failed to inhibit LH- or forskolin-stimulated cAMP levels in cells preincubated with PMA. It is concluded that SRIF-14 inhibits hormone-stimulated cAMP induction in the porcine ovary. LH-induced protein kinase C activation may be physiologically important to alleviate the inhibitory effects of SRIF-14.
Journal of Endocrinology (1992) 134, 297–306
Search for other papers by P. E. Walton in
Google Scholar
PubMed
Search for other papers by T. D. Etherton in
Google Scholar
PubMed
ABSTRACT
A specific radioimmunoasay (RIA) was established for an acid-stable insulin-like growth factor-binding protein (IGF-BP) isolated from porcine serum. The RIA recognizes a GH-dependent 150 kDa protein in porcine serum; therefore we postulate that the acid-stable IGF-BP is a component of the high molecular weight IGF-BP in porcine serum.
The IGF-BP concentration was assayed in porcine serum (normal, 2·44 mg/l; hypophysectomized, 0·83 mg/l; serum from a GH-treated pig, 4·72 mg/l), porcine colostrum (2·55 mg/l), milk (0·91 mg/l), and amniotic (1·82–3·14 mg/l), allantoic (2·94–3·58 mg/l) and follicular (2·28 mg/l) fluids.
Serum concentrations of IGF-BP were significantly increased (63%) in pigs chronically injected with porcine GH (pGH) (70 μg/kg body weight per day for 17 days). Concentrations of IGF-BP did not change in porcine serum following acute challenges with pGH (10–1000 μg/kg body weight) or IGF-I (4 or 8 mg per pig).
This is the first report of a specific RIA for the porcine GH-dependent IGF-BP. Our results indicate that this IGF-BP is found in a wide variety of biological fluids and that its concentration appears to be regulated by pGH but not by IGF-I.
Journal of Endocrinology (1989) 120, 153–160
Search for other papers by H Ikawa in
Google Scholar
PubMed
Search for other papers by K Yamamoto in
Google Scholar
PubMed
Search for other papers by Y Takahashi in
Google Scholar
PubMed
Search for other papers by N Ueda in
Google Scholar
PubMed
Search for other papers by Y Hayashi in
Google Scholar
PubMed
Search for other papers by S Yamamoto in
Google Scholar
PubMed
Search for other papers by K Ishimura in
Google Scholar
PubMed
Search for other papers by M Irahara in
Google Scholar
PubMed
Search for other papers by T Aono in
Google Scholar
PubMed
Abstract
Arachidonate 12-lipoxygenase, which oxygenates positions 12 and 13 of arachidonic and linoleic acids, is present in porcine anterior pituitary cells. Colocalization of the 12-lipoxygenase with various pituitary hormones was examined by immunohistochemical double-staining using antibodies against 12-lipoxygenase and various anterior pituitary hormones. Under light microscopy, approximately 7% of the cells producing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were positive for 12-lipoxygenase, whereas the enzyme was detected in less than 2% of the cells producing thyrotrophin, prolactin, growth hormone (GH), and adrenocorticotrophin. In an attempt to examine the participation of 12-lipoxygenase metabolites in pituitary hormone release, we incubated the primary culture of porcine anterior pituitary cells with 12-hydroperoxy-arachidonic acid or 13-hydroperoxy-linoleic acid. Significant stimulation of LH and FSH release by these hydroperoxides was observed at 10 μm in a time-dependent manner. At doses around 10 μm these compounds produced responses of similar magnitude to 1 nm gonadotrophin-releasing hormone (GnRH), but higher concentrations (30 μm) of the compounds were required for GH release. In contrast, 12-hydroxy-arachidonic and 13-hydroxy-linoleic acids were almost ineffective. Furthermore, the gonadotrophin release by 1 nm GnRH was inhibited by nordihydroguaiaretic acid (a lipoxygenase inhibitor) with an IC50 of about 5 μm. Thus, the hydroperoxy (but not hydroxy) products of 12-lipoxygenase may be involved in the release of pituitary hormones especially LH and FSH.
Journal of Endocrinology (1996) 148, 33–41
Search for other papers by K. Rajkumar in
Google Scholar
PubMed
Search for other papers by P. J. Chedrese in
Google Scholar
PubMed
Search for other papers by H. Ly in
Google Scholar
PubMed
Search for other papers by B. D. Murphy in
Google Scholar
PubMed
ABSTRACT
LH, in addition to increasing cyclic AMP (cAMP) in ovarian cells, stimulates phosphoinositide hydrolysis producing inositol trisphosphate and diacylglycerol (DG). DG activates phospholipid- and calcium-dependent protein kinase (PKC). In the present study, we have used both PKC activators and inhibitors to examine the interactions of the PKC pathway on hormone-induced cAMP production in porcine luteal cells. Phorbol 12-myristate 13-acetate (PMA) enhanced LH- and forskolin-induced cAMP production. A time-course study indicated that the facilitatory effect of PMA was greater when added to incubation tubes following addition LH or forskolin. The non-tumour-promoting phorbol ester 4α-phorbol 12,13-didecanoate, which does not stimulate PKC activation, did not facilitate hormone-induced cAMP induction. PKC inhibitors polymyxin B, sphingosine and 1-(5-isoquinolinesulphonyl)-2-methylpiperazine (H7) antagonized the facilitatory effect of PMA on LH-induced cAMP production. The cAMP induction by both LH and forskolin was inhibited in the presence of PKC inhibitors. Polymyxin E, which differs from polymyxin B by a single amino acid and does not inhibit PKC activation, did not inhibit LH- or forskolin-induced cAMP induction.
The results of this study provide evidence for a facilitative action of the PKC effector system on hormonally stimulated cAMP production. Furthermore, PKC may be an important endogenous regulator of adenylate cyclase activity in porcine luteal cells.
Journal of Endocrinology (1991) 130, 273–280
Search for other papers by H. Humphries in
Google Scholar
PubMed
Search for other papers by S. MacNeil in
Google Scholar
PubMed
Search for other papers by D. S. Munro in
Google Scholar
PubMed
Search for other papers by S. Tomlinson in
Google Scholar
PubMed
ABSTRACT
Recent evidence suggests that epidermal growth factor (EGF) may play an important role in the regulation of thyroid growth and function. We have examined the interaction of murine EGF (mEGF) with human and porcine thyroid membranes and compared this with the binding of bovine TSH (bTSH) using 125I-labelled hormones as tracers. The characteristics of the binding of mEGF were found to be similar for human and porcine thyroid membranes. Epidermal growth factor bound with high affinity (affinity constant = 1·4 × 109 l/mol); the density of binding sites was low compared with the TSH receptor. At 37 °C, the binding of 125I-labelled EGF was maximal at 1 h and was saturable in the presence of unlabelled EGF; half-maximal inhibition was at 1 ng EGF/tube (0·5 nmol/l) using 0·5 mg membrane protein/tube. Unlabelled bTSH had no effect on the binding of labelled EGF. Similarly, unlabelled EGF did not affect the binding of labelled TSH; hence it was concluded that mEGF and bTSH bound to independent sites. Epidermal growth factor had no effect on adenylate cyclase activity in membranes prepared from human non-toxic goitre; increasing concentrations of EGF did not affect basal, TSH-stimulated or fluoride-stimulated enzyme activity.
J. Endocr. (1984) 102, 57–61
Search for other papers by S. B. SUFI in
Google Scholar
PubMed
Search for other papers by R. S. TOCCAFONDI in
Google Scholar
PubMed
Search for other papers by P. G. MALAN in
Google Scholar
PubMed
Search for other papers by R. P. EKINS in
Google Scholar
PubMed
SUMMARY
The binding of 125I-labelled thyroxine and tri-iodothyronine to a 100000 g supernatant fraction (cytosol) from homogenates of porcine anterior pituitary lobes was examined. The kinetics of thyroxine binding were studied and the dissociation rate-constant observed at 4 °C was 2·4 × 10−4 s−1. Equilibrium constants of relatively high affinity for both iodothyronine hormones were obtained from Scatchard plots of dose-response data, and were found to be 0·4 × 109 m−1 for tri-iodothyronine and 1·4 × 109 m−1 for thyroxine. Bound [125I]thyroxine could be virtually completely displaced by unlabelled thyroxine, but only partially by unlabelled tri-iodothyronine. From these relative potency experiments it is tentatively suggested that a thyroxine-specific site of low affinity is present in the cytosol. A protein component is probably involved in thyroxine binding, since a decrease in bound hormone was seen only after treatment with proteolytic enzymes.
The thyroxine-binding capacities of anterior pituitary cytosol and porcine serum were similar, and were two or three times greater than the binding capacities of cytosol fractions from either posterior pituitary or brain frontal lobe. These results suggest that thyroxine binding in the anterior pituitary cytosol is unlikely to have resulted solely from contamination by serum thyroxine-binding proteins. Further evidence for this belief was provided by thin-layer chromatographic separation of labelled thyroxine bound to either cytosol or to serum proteins. The possible relevance of these studies to the feedback regulation of thyrotrophin secretion is discussed.
Search for other papers by RS Everett in
Google Scholar
PubMed
Search for other papers by DE Gerrard in
Google Scholar
PubMed
Search for other papers by AL Grant in
Google Scholar
PubMed
Direct DNA injection into porcine skeletal muscle was investigated as an approach for studying roles of locally produced IGF-I on IGF-binding protein (IGFBP) production. To determine parameters for maximal reporter gene expression, and to investigate the effects of dose, time and weaning on exogenous DNA expression, plasmid DNA encoding firefly luciferase under control of a constitutive promoter and enhancer was injected in skeletal muscle of pigs. Results indicate that injected DNA does not migrate beyond 9 mm from injection sites and that 100 microg DNA injections resulted in optimal luciferase activity. Maximum amounts of recombinant protein were observed 3 days after injection, and were reduced by weaning. Using these data, a second DNA injection study was performed using plasmid DNA containing a cDNA insert for epitope-tagged insulin-like growth factor-I (TIGF-I). Significant quantities of TIGF-I were detected by ELISA and confirmed by western blotting. Both IGFBP-2 and IGFBP-2 mRNA were increased in treated muscle compared with controls. We conclude that increased expression of IGF-I in muscle results in increased IGFBP-2. Furthermore, these data indicate that this in vivo approach of gene transfer results in biologically active recombinant protein production in porcine skeletal muscle, and provides an excellent in vivo model for studying the autocrine and (or) paracrine effects of locally produced growth factors in skeletal muscle.
Search for other papers by J. R. Bourke in
Google Scholar
PubMed
Search for other papers by P. A. McGrath in
Google Scholar
PubMed
Search for other papers by G. J. Huxham in
Google Scholar
PubMed
Search for other papers by M. J. Waters in
Google Scholar
PubMed
Search for other papers by S. W. Manley in
Google Scholar
PubMed
ABSTRACT
Cultured porcine thyroid cells maintained in media containing TSH exhibited a membrane potential of −50 mV, and hyperpolarized by about 10 mV within 1 h of the addition of epidermal growth factor (EGF; 10 ng/ml). Follicle cells had depolarized to −45 mV after 4 h of exposure to EGF. Cells maintained in dibutyryl cyclic AMP (dbcAMP) did not alter their membrane potential when exposed to EGF for up to 4 h. Cultures washed to remove the TSH or dbcAMP hyperpolarized to − 75 mV within 30 min, and a reversible depolarization to − 60 mV was observed on addition of EGF. It was concluded that EGF acts as a physiological antagonist of TSH and also exerts a separate depolarizing influence on cultured thyroid cells.
J. Endocr. (1986) 109, 321–324
Search for other papers by N Delorme in
Google Scholar
PubMed
Search for other papers by C Remond in
Google Scholar
PubMed
Search for other papers by H Sartelet in
Google Scholar
PubMed
Search for other papers by E Petitfrere in
Google Scholar
PubMed
Search for other papers by C Clement in
Google Scholar
PubMed
Search for other papers by C Schneider in
Google Scholar
PubMed
Search for other papers by G Bellon in
Google Scholar
PubMed
Search for other papers by A Virion in
Google Scholar
PubMed
Search for other papers by B Haye in
Google Scholar
PubMed
Search for other papers by L Martiny in
Google Scholar
PubMed
Thyrotropin (TSH) and transforming growth factor beta 1 (TGFbeta1) have major roles in the regulation of folliculogenesis and differentiation in thyroid cells. Isolated porcine thyroid cells cultured in the presence of TSH on a plastic surface recover a follicular architecture and exhibit normal functional properties. The addition of TGFbeta1 to the culture medium induces important morphological changes and extracellular matrix remodelling. Similarly, thyroid cells lose their ability to organify iodine and their responsiveness to adenylate cyclase. The aim of this study was to analyse the influence of TGFbeta1 on the functional activity of thyrocytes in suspension culture, independent of follicle disruption. In this system, we demonstrate that TGFbeta1 inhibits expression of thyroperoxidase, NADPH oxidase activity, iodine uptake and, consequently, iodine organification. Moreover, TGFbeta1 decreases basal and TSH-stimulated cAMP production and TSH receptor expression. Taken together, these data converge to demonstrate an essential role of TGFbeta1 in the regulation of the thyroid cell function.
