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Journal Article 2011; 32(6): 769-773 PubMed PMID: 22286790 Citation  Keywords:  Animals, Cells, Cultured, Estradiol:pharmacology, Female, Follicle Stimulating Hormone:secretion, Intracellular Signaling Peptides and Proteins:metabolism, Luteinizing Hormone:secretion, Neuropeptides:metabolism, Orexins, Ovariectomy, Pituitary Gland:cyto.   

OBJECTIVES: Orexin A (OxA) is a regulatory neuropeptide which is involved in the control of various autonomic and neuroendocrine functions. It regulates sleep-wake cycle, food intake and modulates the hypothalamic and pituitary hormones secretion. Orexin A acts through two types of receptors, which proved to exist in the pituitary. This may indicate the possibility of direct action of OxA on the adenohypophysis level. The aim of this study was to evaluate the direct effect of orexin A on gonadotropin (LH and FSH) release from cultured pituitary cells of immature female rats as well as mature female rats (ovariectomized and ovariectomized and estradiol treated rats).

MATERIAL AND METHODS: The effect of 0.1 nM and 100 nM orexin A on LH and FSH release from anterior pituitary cells after 1 h of incubation was examined in immature female rats (IM) as well as mature female (ovariectomized - M/OVX; and ovariectomized and estradiol treated - M/OVX+E2) rats. The concentration of LH and FSH in medium was determined by RIA method.

RESULTS: Orexin A at a dose of 0.1 nM and 100 nM significantly stimulated LH secretion in IM group. In M/OVX group release of LH was inhibited by OxA only in higher dose (100 nM). No effect of orexin A on FSH secretion was found.

CONCLUSIONS: OxA may directly modulate LH secretion from cultured pituitary cells and it has the contradictory effect on LH release in immature and ovariectomized mature female rats....

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Journal Article 2005; 26(4): 377-382 PubMed PMID: 16136005 Citation  Keywords:  Animals, Copper:metabolism, Cyclic AMP:metabolism, Female, Gonadotropin-Releasing Hormone:metabolism, Hydrolysis, Inositol Phosphates:metabolism, Luteinizing Hormone:secretion, Nickel:metabolism, Phosphatidylinositols:metabolism, Pituitary Gland, Anterior.   

: Gonadotropin releasing hormone (GnRH) is an essential factor in the regulation of synthesis and release of pituitary gonadotropins. After binding to specific receptors and coupling with G proteins, it triggers the intracellular signaling involving the synthesis of inositol phosphates and diacylglycerol. Previously we have showed that certain metal complexes with GnRH, i.e. copper (Cu-GnRH) and nickel (Ni-GnRH) are able to bind to the GnRH receptors. The intracellular signalling of these complexes, however, has not been yet elucidated. In this experiment, the ability of the Cu-GnRH and Ni-GnRH complexes to modulate cAMP synthesis and phosphoinositols formation in the pig anterior pituitary cells in vitro was studied. The native GnRH and its metal complexes stimulated the luteinizing hormone (LH) release, but only the effect of Cu-GnRH was found to be a dose-dependent. The metal complexes did not significantly influence inositol phosphates accumulation, while their effect on cAMP synthesis was significantly more potent than that of GnRH alone. We conclude that the Cu-GnRH and Ni-GnRH complexes increase LH release in the porcine pituitary cells although their intracellular signaling is different from that of the native GnRH. It seems that metal complexes with GnRH deserve more attention in further studies....

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