Differences in K+ Permeability Between Cultured Adult and Neonatal Rat Islets of Langerhans in Response to Glucose, Tolbutamide, Diazoxide, and Theophylline

Abstract

The effects of glucose, tolbutamide, and diazoxide on K+ permeability in neonatal and adult rat pancreatic islets, maintained in culture 1 week, were investigated by measuring the 86Rb outflow rate from prelabeled islets. In the absence of glucose, the 86Rb efflux was significantly lower in neonatal than adult islets. Raising the glucose concentration to 2.8, 5.6, 8.3, and 11.1 mM produced a marked reduction in the 86Rb efflux in adult islets but only a minor reduction in neonatal islets. The effect of tolbutamide to reduce, and diazoxide to increase, the 86Rb efflux was also less in neonatal islets. These results are discussed with respect to previously reported differences in insulin secretion from neonatal and adult islets in culture.