Lysophosphatidylcholine Decreases Delayed Rectifier K⁺ Current in Rabbit Coronary Smooth Muscle Cells

Abstract

Lysophosphatidylcholine (LPC), which exists abundantly in lipid fraction of oxidized low density lipoprotein, has been implicated in enhanced agonist-induced contraction and increase of intracellular Ca²⁺. The effect of LPC on the activity of delayed rectifier K⁺ current (I_dK), which is a major determinant of membrane potential and vascular tone under resting condition, was examined in rabbit coronary smooth muscle cells using whole cell patch clamping technique. Application of LPC to the bath solution caused a concentration-dependent inhibition of I_dK, and the concentration to produce half-maximal inhibition was 1.51 μM. This effect of LPC on I_dK was readily reversed after washout of LPC in the bath. The steady-state voltage dependence of I_dK was shifted to positive direction by both extra- and intracellular application of LPC. Staurosporine (100 nM) pretreatment significantly suppressed the LPC-induced inhibition of I_dK. These results suggest that LPC inhibits I_dK in rabbit coronary smooth muscle cells by a pathway that involves protein kinase C, and the LPC-induced inhibition of I_dK may be, at least in part, responsible for the abnormal vascular reactivity in atherosclerotic coronary artery.