Effects of endothelin on porcine coronary arterial strips

Endothelin, a novel endothelium derived 21-residue vasoconstrictor peptide synthesized by Peninsula Laboratories, provoked a concentration-dependent contraction of porcine coronary arterial strips. EC50 value for endothelin was 14 +/- SD 4 nmol/L (n = 6), and significantly lower than the values for 5-hydroxytryptamine (5-HT, 0.28 +/- 0.07 mumol/L, n = 6) and 15-methyl-prostaglandin F2 alpha (15-methyl-PGF2 alpha, 4 +/- 3 mumol/L, n = 7). The maximal increase in tension caused by endothelin was 5.4 +/- 1.1 g, being much greater than that induced by 5-HT (3.7 +/- 0.8 g, P less than 0.05) and 15-methyl-PGF2 alpha (3.7 +/- 0.6 g, P less than 0.01). The changes in tension provoked by endothelin (2-20 nmol/L) were attenuated significantly after pretreated with tetrodotoxin (TTX, 30 mumol/L, P less than 0.05 or 0.01). The results suggest that endothelin is one of the most potent vasoconstrictive agents, and its action is partially related to voltage-sensitive Na+ channel in the cell membrane.