A Study of the Relaxed Mechanisms Induced by Novokinin in the Isolated Porcine Coronary Artery Ring Segments.

Novokinin is a vasorelaxing peptide designed according to the structure of ovokinin(2-7) that is released from ovalbumin by chymotryptic digestion. It has attracted much attention due to its variety of pharmacological and biological characteristics. The purpose of this research was to judge the effect and the mechanism of novokinin on porcine coronary arteries. The isometrical tension of coronary arterial rings getted from porcine hearts was measured and its reaction to novokinin (10(-12)-10(-5) mol/L) was observed. It was found that novokinin inhibited the vasocontractivity to KCl and CaCl2 and evidently decreased the isomeric tensile force of both quiescent and prostaglandin F2 alpha (PGF2 alpha) precontracted porcine coronary arterial ring segments. This relaxing effect of novokinin on porcine coronary arteries was apparently cutted down by getting rid of endothelium, and by the addition of methylene blue, N-nitro-L-arginine (L-NNA) or indomethacin, but not by propranolol. Novokini also inhibited the KCl- and CaCl2-induced vasocontraction. The experimental results show that relaxed effect of novokinin on porcine coronary arteries might relate to the function of nitric oxide (NO), cyclic guanosine monophosphate (cGMP) and the synthesis of prostaglandin, but not involve adrenergic beta-receptor.