UROKINASE PLASMINOGEN-ACTIVATOR ACTIVITY IS INCREASED IN THE MYOCARDIUM DURING CORONARY-ARTERY OCCLUSION

We have previously demonstrated that collateral development takes plac e in a swine model of coronary artery occlusion. In this report we hav e examined the effect of coronary artery occlusion on urokinase and ti ssue plasminogen activator activity in the myocardium. Urokinase activ ity was increased four-fold in the ischemic heart compared to sham and unoperated controls. In contrast, the level of tissue plasminogen act ivator activity remained relatively constant. The increase in urokinas e activity was associated with an upregulation of urokinase RNA levels and of the RNAs corresponding to the plasminogen activator inhibitors , PAI I and IL. Urokinase has been shown to be an important angiogenic protease both in vivo and in cultured cells. Its increase during coll ateral development suggests that urokinase may play a role in angiogen esis in the ischemic heart.