Endothelin‐1 Signaling in Coronary Arteriolar Constriction

Abstract

Endothelin‐1 (ET‐1) is a potent vasoconstrictor implicated in coronary heart diseases, but its signaling for vasoconstriction remains elusive. Herein, we probed the role of voltage‐gated Ca2+ channels (VGCCs), phospholipase C (PLC), myosin light chain kinase (MLCK), protein kinase C (PKC) and Rho kinase (ROCK) in the porcine coronary arteriolar response to a pathologic dose of ET‐1 (0.1 nM). Isolated coronary arterioles (~70 μm) constricted to ET‐1 (from 52±3% to 32±3% max. diameter) in a manner sensitive to ETA receptor blocker BQ123, zero‐extraluminal Ca2+, and PLC inhibitor U73122. Inhibiting VGCCs by nifedipine or MLCK by ML‐9 abolished basal tone but did not affect ET‐1 response. ROCK inhibitor H1152 blocked vasoconstrictions to ET‐1 but not PKC activator PDBu. Broad‐spectrum PKC inhibitor Gö6983 blocked vasoconstriction to PDBu but not ET‐1. The PKC‐activated CPI‐17 protein was undetectable in arterioles. Moreover, ET‐1 elicited phosphorylation of myosin‐binding subunit (MBS) in H1152‐sensitive manner. ROCK2, but not ROCK1, siRNA inhibited vasoconstriction to ET‐1. We conclude that VGCCs and MLCK contribute to the generation of basal tone rather than the constriction to ET‐1. The sequential activation of ETA receptors, PLC and the VGCC‐independent Ca2+ entry leads to vasoconstriction to ET‐1 via a pathway involved in ROCK2‐associated MBS phosphorylation independent of PKC signaling.