Long-Term Effect of Prolactin Treatment on Glucose-Induced Insulin Secretion in Cultured Neonatal Rat Islets

Insulin secretion and ⁴⁵Ca²⁺ uptake and efflux were studied in neonatal rat islets maintained in culture for 7 or 19 days in the absence or presence of prolactin (PRL). Insulin secretion in response to glucose (G), leucine (Leu), arginine (Arg) and carbachol (Cch) was augmented after 7 and 19 days in culture, compared to basal secretion (G 2.8 mM), in both PRL-treated and control islets. However, the increase in insulin secretion induced by the above secretagogues was higher in islets cultured in the presence of PRL for 19 days. In PRL-treated islets, the ⁴⁵Ca²⁺ content after a 5 min incubation in the presence of G, Leu, Arg and Cch was significantly higher than the control only in islets cultured for 19 days. Except with Arg, the ⁴⁵Ca²⁺ uptake in PRL-treated islets after a 90 min incubation was also significantly higher than the control only in islets cultured for 19 days. Finally, Leu-induced alterations in the ⁴⁵Ca²⁺ efflux were higher in PRL-treated than in control islets cultured for 7 or 19 days. In the absence of external Ca²⁺, the reduction in ⁴⁵Ca²⁺ efflux induced by glucose was also significantly higher in PRL-treated than in control islets. This 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 potentiated even more if the treatment is prolonged.

Key words

Neonatal Rat Islets - PRL - Insulin Secretion - Calcium