Enzymatic activation of endothelial protease-activated receptors is dependent on artery diameter in human and porcine isolated coronary arteries

Abstract

1. Protease-activated receptor (PAR)-mediated vascular relaxations have been compared in coronary arteries of different diameters isolated from both humans and pigs. 2. Thrombin, trypsin, and the PAR1-activating peptide, TFLLR, all caused concentration-dependent relaxation of both large (epicardial; ∼2 mm internal diameter) and small (intramyocardial; ∼200 μm internal diameter) human coronary arteries. EC50 values for thrombin (0.006 u ml-1 in epicardial, 1.69 u ml-1 in intramyocardial) and trypsin (0.02 u ml-1 in epicardial, 1.05 u ml-1 in intramyocardial) were significantly (P<0.01) greater in intramyocardial arteries. By contrast, EC50 values for TFLLR were not different between epicardia..