ET-1 is a potent vasoconstrictor peptide derived from endothelial cells. It plays a role in regulation of cardiovascular functions. The binding of ET-1 to G-protein coupled receptor triggers a signal transduction cascade leading to activation of the protein kinase C (PKC). PKC inhibitor potentially reverses the up regulation of ET-1. The enhanced ET-1 expression associated with the activation of PKC occurs in early diabetes.