Protective effect of the new antiplatelet agent 2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo[1,5-a]pyridine on myocardial damage due to coronary occlusion and reperfusion in rabbit.

The effects of KC-764 (2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo[1,5-a]pyridine, CAS 94457-09-7) on infarct size, myeloperoxidase (MPO) activity and plasma prostanoid levels were studied using coronary artery occlusion (1 h)-reperfusion (3 h) model in rabbits, comparing with acetylsalicylic acid (ASA). Myocardial infarct size, MPO activity in the infarcted region and plasma glutamate oxalo-acetate transaminase, lactate dehydrogenase and creatine kinase were significantly suppressed by treatment with KC-764 (2 mg/kg i.v.), but not by ASA (10 mg/kg i.v.). KC-764 completely depressed the increase in plasma TXB2 level during occlusion-reperfusion with a little influence on plasma 6-keto-PGF1 alpha. Thus, the ratio of 6-keto-PGF1 alpha to TXB2 levels was increased by KC-764. On the other hand, ASA treatment depressed both plasma TXB2 and 6-keto-PGF1 alpha levels to the same extent. The in vitro study with guinea-pig neutrophils showed that KC-764 reduced the chemotaxis induced by formyl-methionyl-leucyl- phenylalanine at 3 x 10(7)-3 x 10(-6) mol/l, while ASA did not influence the neutrophil chemotaxis. These results suggest that KC-764 may salvage the damaged ischemic myocardium by the selective inhibition of TXA2 synthesis and the suppression of leukocyte migration.