The glucoregulatory hormones insulin and glucagon are released from the β-and α-cells of
the pancreatic islets. In both cell types, secretion is secondary to firing of action potentials,
Ca2+-influx via voltage-gated Ca2+-channels, elevation of [Ca2+] i and initiation of Ca2+-
dependent exocytosis. Here we discuss the mechanisms that underlie the reciprocal
regulation of insulin and glucagon secretion by changes in plasma glucose, the roles played
by different types of voltage-gated Ca2+-channel present in α-and β-cells and the …