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Studies have shown that mastoparan and other amphiphilic peptides induce exocytosis of hormones from anterior pituitary cells. We have studied the effect of mastoparan on the secretion of prolactin from cultured rat anterior pituitary cells and on the concomitant functional status of signal-transducing pathways in lactotroph-enriched cell cultures. Mastoparan stimulation of prolactin secretion was dose-dependent, time-dependent, reversible and required the presence of calcium. Pretreatment of pituitary cell cultures with cholera and pertussis toxin had no effect on the secretory response, whereas encapsulation of guanosine 5-[β-thio]diphosphate (GDP-β-S) by reversible electropermeabilization inhibited mastoparan-stimulated secretion. Incubation of mastoparan with myo[³H]inositol-labelled lactotroph-enriched anterior pituitary cell cultures resulted in increased formation of inositol phosphates compared with control cells, and encapsulation of GDP-β-S blocked mastoparan-induced inositol lipid hydrolysis. Mastoparan caused translocation of protein kinase C activity from a soluble to a membrane-attached form. Mastoparan was able to increase the intracellular Ca²⁺ concentration in Fura-2-loaded individual lactotrophs. Omission of Ca²⁺ from the extracellular medium did not change the Ca²⁺ response in lactotrophs when stimulated with mastoparan.

On the basis of these results it is concluded that mastoparan-induced release of prolactin is preceded by activation of the inositol(1,4,5)trisphosphate/diacylglycerol pathway with resulting translocation of protein kinase activity and increment in intracellular Ca²⁺. However, other signal-transducing pathways may be involved in the secretory process.

Journal of Endocrinology (1994) 142, 9–18

This article has been cited by other articles:

				Y. Yajima, K. Uchino, H. Ito, and S. Kawashima Mastoparan-Stimulated Prolactin Secretion in Rat Pituitary GH3 Cells Involves Activation of Gq/11 Proteins Endocrinology, May 1, 1997; 138(5): 1949 - 1958. [Abstract] [Full Text] [PDF]