RESUMO
Acute ischemia followed by reperfusion in skeletal muscle is associated with tissue edema and necrosis. The purpose of this study was to demonstrate superficial femoral artery endothelial injury following complete ischemia with reperfusion. New Zealand white rabbits underwent total devascularization of one hindlimb for 3 hr followed by 0, 1, and 2 hr of reperfusion. Control rabbits underwent a sham operation. Superficial femoral artery rings were then studied for acetylcholine induced relaxation in vitro. The response to acetylcholine was measured as percentage relaxation at three incremental doses (1 x 10(-7) , 3 x 10(-7) and 5 x 10(-7) M). The ischemia-only (26.30 +/- 7.07, 62.63 +/- 8.64, 88.08 +/- 5.25%) and the 1-hr reperfusion group (19.35 +/- 12.99, 39.24 +/- 15.78, 62.01 +/- 14.03%) showed no significant difference (P > or = 0.05, Student's t test) in relaxation as compared to the control group (13.73 +/- 2.11, 47.88 +/- 7.23, 72.44 +/- 9.00%). The 2-hr reperfusion group (6.10 +/- 1.02, 15.33 +/- 2.56, 34.67 +/- 6.31%), however, had a significant loss of relaxation at all three doses of acetylcholine compared to that seen in the control group (P < or = 0.05, Student's t test). In this model of complete ischemia, superficial femoral artery rings lose their ability to relax in response to acetylcholine following 3 hr of ischemia and 2 hr of reperfusion, demonstrating endothelial injury. However, immediately after 3 hr of ischemia or ischemia followed by only 1 hr of reperfusion, superficial femoral artery rings did not lose their ability to relax in response to acetylcholine. This study identifies a window of opportunity for therapeutic intervention after ischemia and prior to endothelial injury from reperfusion.
