Activin A increases intracellular free calcium concentrations in rat pancreatic islets

Abstract

Activin A stimulated insulin secretion in rat pancreatic islets, an effect that was attenuated by reduction of extracellular Ca²⁺ and abolished by either nitrendipine or verapamil. Activin A increased intracellular the free Ca²⁺ concentration, [Ca²⁺]_i in fura-2-loaded islets. Activin A-mediated elevation of [Ca²⁺]_i was abolished by the reduction of extracellular Ca²⁺ or the addition of nifedipine. In addition, activin A did not increase [Ca²⁺]_i in the presence of diazoxide, an opener of ATP-sensitive K⁺ channels. These results suggest that activin A increases insulin secretion by stimulating Ca²⁺ entry.