Prolactin induces maturation of glucose sensing mechanisms in cultured neonatal rat islets
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The effects of PRL treatment on insulin content and secretion, and86Rb and45Ca fluxes from neonatal rat islets maintained in culture for 7-9 days were studied. PRL treatment enhanced islet insulin content by 40% and enhanced early insulin secretion evoked by 16.7 mM glucose. Insulin release stimulated by oxotremorine-M, a muscarinic agonist, in the presence of glucose (8.3 or 16.7 mM) was unchanged by PRL treatment. However, PRL treatment potentiated phorbol 12, 13-dibutyrate-stimulated insulin secretion in the presence of the above glucose concentrations. PRL treatment potentiated the reduction in86Rb efflux induced by glucose or tolbutamide and enhanced the increase in86Rb efflux evoked by diazoxide. PRL treatment slightly potentiated the increment in45Ca uptake induced by high concentrations of K+, but failed to affect the increment evoked by 16.7 mM glucose. Since glucose-induced45Ca uptake was not affected by PRL, we suggest that the enhancement in first phase insulin secretion evoked by glucose in the PRL-treated islets occurs at a step in the secretory process that may involve protein kinase-C. These data further support observations that PRL treatment increases islet sensitivity to glucose. © 1993 by The Endocrine Society.