Mechanism of C-type natriuretic peptide-induced endothelial cell hyperpolarization

natriuretic peptide (CNP) has a demonstrated hyperpolarizing effect on vascular smooth muscle cells. However, its autocrine function, includ-ing its electrophysiological effect on endothelial cells, is not known. Here, we report the effect of CNP on the membrane potential (Em) of pulmonary microvascular endothelial cells and describe its target receptors, second messengers, and ion channels. We measured changes in Em using fluorescence imaging and perforated patch-clamping tech-niques. In imaging experiments, samples were preincubated in the potentiometric dye DiBAC4(3), and subsequently exposed to CNP in the presence of selective inhibitors of ion channels or second mes-sengers. CNP exposure induced a dose-dependent decrease in fluo-rescence, indicating that CNP induces endothelial cell hyperpolariza-tion. CNP-induced hyperpolarization was inhibited by the K channel blockers, tetraethylammonium or iberiotoxin, the nonspecific cation channel blocker, La3, or by depletion or repletion of extracellula