Recombinant Pro-Urokinase Requires Heparin for Optimal Clot Lysis and Restoration of Blood Flow in a Canine Femoral Artery Thrombosis Model

Abstract

Heparin is often used as an adjunct to thrombolytic therapy in order to prevent reocclusion of the patent vessels in patients with thrombotic disease. Controversy exists as to whether heparin is required for effective clot lysis with tissue-type plasminogen activator, while in vitro data and small scale clinical trials have suggested an enhancement of pro-urokinase efficacy by heparin. The present study was conducted to determine whether heparin pre-treatment is required to produce optimal clot lysis and blood flow restoration in response to recombinant pro-urokinase (r-proUK). In four groups of dogs, blood clots labelled with 125Iodine were formed in the femoral artery and were monitored continuously for loss of counts as an indicator of clot lysis. Femoral artery blood flow was measured simultaneously. Group 1 received vehicle (n = 5), while group 2 was given vehicle + heparin (n = 6; 500 U bolus + 350 U/h). This dose of heparin increased the activated partial thromboplastin time (APTT) by at least 1.5 times the control level for the 4 h observation period. Group 3 received r-proUK alone at a dose of 100,000 U/kg (50% given as a 1-min bolus injection, 50% as a 30 min infusion) (n = 8), while group 4 was treated with the same dose of r-proUK in the presence of heparin as described (n = 8).2