Abstract
We have compared the effect of two thrombolytic agents, i. e., single chain urokinase-type plasminogen activator (scu-PA) and tissue type plasminogen activator (t-PA), on the stenosis rate of PTCA catheter-induced injury of the coronary artery in dogs. The stenosis rate of the injured vessel as observed by coronary artery angiography four weeks after the injury was found to be reduced in the scu-PA-treated animals, but increased in the t-PA-treated animals, as compared with the control animals given physiological saline alone. These results were confirmed histologically and by assessment of the intima/media ratio, as well, and the difference in the stenosis ratios between the two drug-treated groups was statistically significant. Interestingly, scu-PA was found to promote proliferation of endothelial cells but not that of smooth muscle cells, whereas t-PA promoted proliferation of smooth muscle cells but not that of endothelial cells. These results seem to imply that scu-PA may be engaged in an early stage of repair of blood vessel injuries through endothelial cell proliferation. Furthermore, lack of smooth muscle cell proliferation at loci in the scu-PA-treated animals seems to be relevant to the low stenosis rate in this group as compared with the t-PA-treated group.
