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Endothelins (ETs) are a family of vasoactive peptides that may be involved in granulosa cell (GC) luteinization or follicular maturation. However, the precise role of ET in ovarian physiology remains unknown. We have investigated whether the rat GC is a site of ET reception and have characterized the antigonadotropic effect of ET in cultured GC from(More)
The hypothalamic hormone gonadotropin-releasing hormone (GnRH) has been found in milk of man, cow, and rat. Radioimmunoassays of acidified milk indicate concentrations of GnRH ranging between 0.1 and 3 nanograms per milliliter. Multistep extractions, followed by electrophoresis, reveal gonadotropin-releasing activity in the fraction that comigrates with the(More)
We have studied the association between protein tyrosine phosphorylation and the mitogenic effect induced by platelet-derived growth factor (PDGF) in the osteoblast-like cell line MC3T3-E1. PDGF caused a dose-dependent increase in [3H]thymidine incorporation in MC3T3-E1 cells, reaching a plateau at 10 ng/ml. Vanadate, a potent phosphatase inhibitor, induced(More)
A highly purified preparation of rat liver insulin receptor obtained by affinity chromatography has two main peptide components with M, values of approximately 135,000 and 45,000. Peptide maps of the two components after digestion with chymotrypsin indicate the 45,000-dalton component i s not a fragment of the 135,000-dalton component. Antibodies prepared(More)
The synthetic peptide NH2-Tyr-Pro-Phe-Pro-CONH2 (morphiceptin), which is the amide of a fragment of the milk protein beta-casein, has morphinelike activities and is highly specific for morphine (mu) receptors but not for enkephalin (delta) receptors. It is as active as morphine in the guinea pig ileum but much less active in the mouse and rat vas deferens.(More)
Binding studies with the structurally similar vasoconstrictor peptides 125I-endothelin and 125I-sarafotoxin b, the former of mammalian origin and the latter derived from snake venom, reveal their mutually exclusive binding to rat atrium and various regions of the rat brain. In these tissues endothelin, like sarafotoxin, induces phosphoinositide hydrolysis(More)
The mitogenic activity of endothelin (ET) was studied in osteoblast-like cells, MC3T3-E1. [3H] Thymidine incorporation induced by ET was markedly lower than that of platelet-derived growth factor (PDGF). ET synergistically stimulated [3H] thymidine incorporation induced by PDGF with an apparent ED50 value of 2.5 nM. Treatment of MC3T3-E1 cells with ET and(More)