Calcium dependent and independent endothelin-1-induced contraction of human omentum vessels.

Endothelin-1, an endothelium derived vasoconstrictor peptide, induced concentration-dependent contraction of isolated human omental resistance arteries. Pre-treatment with the calcium antagonist nicardipine or calcium depletion caused a significant reduction but did not abolish the contractile response. However, when calcium depletion was combined with pretreatment with the protein kinase C inhibitor (H7), endothelin-1 failed to produce a contraction. This study shows that a large component of endothelin-1 contraction is calcium-dependent, involving activation of dihydropyridine-sensitive voltage-dependent calcium channels but in addition there is a calcium-independent component produced by protein kinase C activation.