20-hydroxyeicosatetraenoic acid-induced vasoconstriction and inhibition of potassium current in cerebral vascular smooth muscle is dependent on activation of protein kinase C

20-Hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450 metabolite of arachidonic acid, is a potent vasoconstrictor, and has been implicated in the myogenic activation of renal and cerebral arteries. We examined the role of protein kinase C (PKC) in the signal transduction pathway by which 20-HETE induces vasoconstriction and inhibition of whole-cell K+ current in cat cerebral vascular smooth muscle, 20-HETE induced a concentration-dependent constriction in isolated pressurized cat middle cerebral arteries (-29 +/- 8% at 1 mu M). However, in the presence of an N-myristoylated PKC pseudosubstrate inhibitor peptide (Myr Psi PKC-I(19-27)) 20-HETE induced a concentration-dependent vasodilation (26 +/- 4% at 1 mu M). In whole-cell voltage clamp studies, application of 20-HETE inhibited whole-cell K+ current recorded in cat cerebral vascular smooth muscle cells, an effect that was attenuated by Myr Psi PKC-I(19-27). Further evidence for the role of PKC activation in response to 20-HETE is the finding that 20-HETE increased the phosphorylation of myristoylated, alanine rich PKC substrate in cultured cat cerebral vascular smooth muscle cells in a concentration-and PKC-dependent manner. These data provide evidence that PKC is an integral part of the signal transduction pathway by which 20-HETE elicits vasoconstriction of cerebral arteries and inhibition of whole-cell K+ current in cat cerebral vascular smooth muscle.