Rho‐Kinase‐Mediated Suppression of KDR Current in Cerebral Arteries Requires an Intact Actin Cytoskeleton

This study examined the role of the actin cytoskeleton in Rho‐kinase‐mediated suppression of the delayed rectifier K + (K DR ) current in cerebral arteries. Myocytes from rat cerebral arteries were enzymatically isolated and whole cell K DR currents monitored using conventional patch clamp electrophysiology. At +40 mV, the K DR current averaged 19.8 ± 1.6 pA/pF (mean ± SE) and was potently inhibited by uridine triphosphate (UTP; 30 µM). Consistent with past observations, K DR current suppression was blocked by the Rho‐kinase inhibitors H‐1152 (300 nM) and Y‐27632 (30 µM). Likewise, disruption of the actin cytoskeleton using cytochalasin D (10 µM) or latrunculin A (10 nM) abolished the ability of UTP to suppress K DR . In intact cerebral arteries, UTP induced actin polymerization in a Rho‐kinase‐dependent manner, suggesting that Rho‐mediated actin reorganization could play a role in the modulation of K DR current. Using pressure myography techniques, UTP‐induced depolarization and constriction of cerebral arteries were found to be significantly reduced following Rho‐kinase inhibition with H‐1152, and following the disruption of the actin cytoskeleton using cytochalasin D or latrunculin A. We conclude from our electrophysiological, biochemical, and functional observations that Rho‐kinase mediated alteration of the actin cytoskeleton likely underlies the inhibition of K DR current by UTP, ultimately contributing to the depolarization and constriction of cerebral arteries.