Role of Tyrosine Kinase and PKC in the Vasoconstrictor Response to 20-HETE in Renal Arterioles

The present study examined the hypothesis that activation of protein kinase C (PKC), components of the mitogen-activated protein (MAP) kinase pathway, or both contributes to the inhibitory effects of 20-hydroxyeicosatetraenoic acid (20-HETE) on K activity and its vasoconstrictor response in renal arterioles. 20-HETE (0.1 to 50 [micro sign]mol/L) dose-dependently produced a 30% increase in PKC activity and a fivefold rise in the expression of active extracellular signal-regulated kinase 1 (ERK1) and ERK2 proteins in renal microvessels. 20-HETE (0.01 to 1 [micro sign]mol/L) reduced the diameter of isolated perfused renal interlobular arterioles by 33 +/- 2%. Blockade of PKC activity with an N-myristoylated PKC pseudosubstrate inhibitor (Myr-PKCi, 100 [micro sign]mol/L) or calphostin C (0.5 [micro sign]mol/L) had no significant effect on the vasoconstrictor response to 20-HETE. In contrast, the tyrosine kinase inhibitors genistein (30 [micro sign]mol/L) and tyrphostin 25 (10 [micro sign]mol/L) reduced the response to 20-HETE by 76.5 +/- 2.1% and 67.5 +/- 1.8%, respectively. A specific inhibitor of mitogen-activated extracellular signal-regulated kinase (MEK), PD98059, had no effect on the vasoconstrictor response to 20-HETE. In cell-attached patches on renal vascular smooth muscle cells, 20-HETE reduced the open state probability of a large-conductance K channel (from 0.0026 +/- 0.0004 to 0.0006 +/- 0.0001). The Myr-PKCi (100 [micro sign]mol/L) did not alter the inhibitory effects of 20-HETE on this channel. In contrast, the tyrosine kinase inhibitor genistein (30 [micro sign]mol/L) blocked the inhibitory effects of 20-HETE on the large-conductance K channel. These data suggest that 20-HETE activates the MAP kinase system in renal arterioles and that the activation of a tyrosine kinase, which is proximal to MEK in this cascade, contributes to the inhibitory effects of 20-HETE on K activity and its vasoconstrictor effects in the renal arterioles. (Hypertension. 1999;33[part II]:414-418.)