Requirements for the beneficial effect of long-term incubation with growth hormone on insulin secretion from isolated human fetal islets

Effect of human somatotropin hormone on cultured rat islets

Because growth hormone (GH) improves the insulin secretion capacity of isolated human fetal islets in vitro, we sought to show that it positively influences isolated rat islets. Islets isolated from Wistar albino rats by a modified automated system were cultured in media containing 87% RPMI 1640, 10% FCS, 2% antibiotic-antimycotic, and 1% L-glutamine for 12 +/- 2 days. The cultured islets were divided into two groups: growth hormone negative (Group I) and growth hormone positive (Group II). On the 5th day we observed a decrease in the islet cell counts in both groups (Group I 28% versus Group II 45%). On the 10th day, the decrease continued in the GH-negative group (59%), while the count remained stable in the GH-positive group. The viability of rat islets was determined by fluorescein diacetate (FDA) plus propidium iodide (PI) staining. In comparison to the peripheral green, central orange-red staining pattern of Group I islets upon fluorescent microscopy, Group II showed more compact islets. Cultured islets seemed to be brighter than those without GH in the cultured islets. In conclusion, we observed that 2 weeks of incubation in the presence of GH acts positively on cultured rat islets for both their amount and their viability.