Isometric contraction to direct supramaximal tetanic stimulation of the anterior tibialis (AT) muscle was measured in 50 New Zealand White rabbits after ischemia and reperfusion. Ischemia was produced unilaterally by collateral ligation and temporary inflow control until AT muscle function decreased to < 5% of contralateral (control) AT muscle and the ischemic interval was recorded. Reperfusion was carried out in one of the following ways: group I (n = 20), release of vascular clamps (blood reperfusion [BR]); group II (n = 10), release of vascular clamps and simultaneous intraarterial administration of 50,000 units of urokinase (urokinase reperfusion [UR]); group III (n = 10), release of vascular clamps and simultaneous administration of 50,000 units of urokinase and 28 mg (5 units) of purified rabbit plasminogen (urokinase plasminogen reperfusion [UPR]); and group IV (n = 10), animals defibrinated to < 50 mg/dl with ancrod prior to ischemia and received BR (ancrod blood reperfusion [ABR]). During reperfusion, function was recorded every 60 min for 2 hr. Recovery of experimental muscle function is expressed as the percentage of contralateral control limb function. The mean ischemic interval (mean +/- SEM), to achieve < 5% of contralateral control limb function, was 206.7 +/- 9.9, 209.5 +/- 16.6, 221.7 +/- 12.5, and 272.0 +/- 14.2 min for animals in groups I-IV, respectively. The mean experimental muscle function (mean +/- SEM) following the ischemic interval was 3.2 +/- 0.8, 4.5 +/- 1.4, 4.4 +/- 1.2, and 3.3 +/- 1.0 for groups I-IV, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)