Facilitated calcium mobilization and inositol phosphate production in the priming effect of LH-releasing hormone in the rat

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Abstract
The ability of LHRH to induce Ca2+ mobilization and production of inositol phosphates in rat anterior pituitary tissue in vitro was investigated in relation to the self-priming effect of LHRH. Prior exposure to LHRH (which caused a characteristic potentiation of subsequent secretory responses) specifically enhanced LHRH-induced inositol phosphate production and mobilization of intracellular Ca2+ stores. LHRH-induced influx of Ca2+ through dihydropyridinesensitive Ca2+ channels was unaltered, as was ligand binding to LHRH receptors. These data suggest that a novel facilitation of signalling may occur in the phospho-inositide-Ca2+ mobilization response mechanism during LHRH priming, and that this may represent an important means of regulating cellular responsiveness in gonadotrophs. J. Endocr. (1988) 119, 293–301