LONG-TERM EFFECT OF PROLACTIN TREATMENT ON GLUCOSE-INDUCED INSULIN-SECRETION IN CULTURED NEONATAL RAT ISLETS

Insulin secretion and Ca-45(2+) uptake and efflux were studied in neon atal rat islets maintained in culture for 7 or 19 days in the absence or presence of prolactin (PRL). Insulin secretion in response to gluco se (G), leucine (Leu), arginine (Arg) and carbachol (Cch) was augmente d after 7 and 19 days in culture, compared to basal secretion (G 2.8 m M), in both PRL-treated and control islets, However, the increase in i nsulin secretion induced by the above secretagogues was higher in isle ts cultured in the presence of PRL for 19 days. In PRL-treated islets, the Ca-45(2+) content after a 5 min incubation in the presence of G, Leu, Arg and Cch was significantly higher than the control only in isl ets cultured for 19 days. Except with Arg, the Ca-45(2+) uptake in PRL -treated islets after a 90 min incubation was also significantly highe r than the control only in islets cultured for 19 days, Finally, Leu-i nduced alterations in the Ca-45(2+) efflux were higher in PRL-treated than in control islets cultured for 7 or 19 days. In the absence of ex ternal Ca2+, the reduction in Ca-45(2+) efflux induced by glucose was also significantly higher in PRL-treated than in control islets. Th is effect was slightly potentiated after 19 days in culture, These data further support the hypothesis that PRL treatment enhances maturation of the secretory mechanism in neonatal islets, This effect can be pote ntiated even more if the treatment is prolonged.