METABOLIC-REGULATION OF INTRACELLULAR CALCIUM-CONCENTRATION IN MOUSE PANCREATIC-ISLETS OF LANGERHANS

Intracellular Ca2+ concentration ([Ca2+](i)) handling during K+-induce d Ca2+ loads was studied in single islets of Langerhans. K+-induced de polarization caused a rapid and transient rise in [Ca2+](i). After Kremoval [Ca2+](i) declined with a time course usually fitted by the su m of two exponential functions. Partial Naf removal increased the rest ing [Ca2+](i) level, indicating the existence of a Na+/Ca2+ exchange, but only slightly impaired the recovery from Ca2+ loads. Metabolic poi soning with CN-increased the resting Ca2+ level and slowed down the re covery from Ca2+ loads. Removal of external Na+ in islets poisoned wit h CN- strongly inhibited Ca2+ removal mechanisms. An increase in the g lucose concentration from 0 to 16 mM (in the presence of diazoxide) re sulted in a decrease in the resting [Ca2+](i) and an acceleration of [ Ca2+](i) recovery from K+ loads. These results suggest that the main m echanism responsible for Ca2+ homeostasis is dependent on metabolic en ergy and that such energy can be provided by glucose metabolism.