Inhibition of salmon calcitonin on secretion of progesterone and GnRH-stimulated pituitary luteinizing hormone

Abstract

The effects of salmon calcitonin (sCT) on the production of progesterone and secretion of luteinizing hormone (LH) were examined in female rats. Diestrous rats were intravenously injected with saline, sCT, human chorionic gonadotropin (hCG), or hCG plus sCT. Ovariectomized (Ovx) rats were injected with saline or sCT. In the in vitro experiments, granulosa cells and anterior pituitary glands (APs) were incubated with the tested drugs. Plasma LH levels of Ovx rats were reduced by sCT injection. Administration of sCT decreased the basal and hCG-stimulated progesterone release in vivo and in vitro. 8-Bromo-cAMP dose dependently increased progesterone production but did not alter the inhibitory effect of sCT. H-89 did not potentiate the inhibitory effect of sCT. Higher doses of 25-hydroxycholesterol and pregnenolone stimulated progesterone production and diminished the inhibitory effects of sCT. sCT did not decrease basal release of LH by APs, but pretreatment of sCT decreased gonadotropin-releasing hormone (GnRH)-stimulated LH secretion. These results suggested that sCT inhibits progesterone production in rats by preventing the stimulatory effect of GnRH on LH release in rat APs and acting directly on ovarian granulosa cells to decrease the activities of post-cAMP pathway and steroidogenic enzymes.

Calcitonin Functions Both as a Hypocalcemic Hormone and Stimulator of Steroid Production and Oocyte Maturation in Ovarian Follicles of Common Carp, Cyprinus carpio

“…Binding of CT with membrane receptors was found to be saturable with high affinity (Bmax, 1.2 pmol/mg protein, Kd 48.8 pmol/L). Available information on the presence of CT-binding sites and sCT-induced inhibition of progesterone secretion in rat granulosa cells indicates a physiological role of CT at ovarian levels in mammals (Tsai et al, 1999). Our finding is the first report of the presence of sCT receptor in fish ovary apart from its presence in gills.…”

“…Wang et al, (1994) found that www.intechopen.com CT-like peptides, human CT, salmon CT and CT-gene related peptide inhibit spontaneous and gonadotropin-stimulated testosterone secretion by acing directly on testes and also by reducing the release of pituitary luteinizing hormone (LH). Inhibition of salmon CT on secretion of progesterone-and gonadatropin-releasing hormone (GnRH)-stimulated release of pituitary LH in rat also has been documented (Tsai et al, 1999). Very recently, we also reported for stimulation of salmon CT on secretion of 17β-estradiol by the ovarian follicles of common carp C. carpio (Paul et al, 2008).…”

Downregulation of progesterone biosynthesis in rat granulosa cells by adlay (Coix lachryma-jobi L. var. ma-yuen Stapf.) bran extracts

“…The preparation of granulosa cells was modified from the method described elsewhere. 20,21 The immature female rats (22-25 days of age) were injected subcutaneously with PMSG (15 IU/rat). After 48 h, rats were killed by cervical dislocation.…”

Direct inhibitory effect of digitalis on progesterone release from rat granulosa cells

“…The preparation of granulosa cells was modi®ed from the method described elsewhere (Hwang et al, 1996;Tsai et al, 1999). The immature female rats 22 ± 25 days of age were injected subcutaneously with PMSG (15 iu rat…”