Hypothermia relieves oxidative stress in reperfused skeletal muscle following partial ischemia

The impact of hypothermia on reperfusion-associated oxidative stress in postischemic skeletal muscle was evaluated in a small animal model of high-grade partial ischemia. The infrarenal aorta of heparinized Sprague-Dawley rats was clamped for 90 min, declamped, and then reperfused for 60 min. Previous characterization of this model with 51Cr-tagged microspheres revealed that hindlimb perfusion during aortic clamping continued at 16.6% of baseline values. Resting transmembrane potential difference (Em) and tissue malondialdehyde (MDA), lactate and high-energy phosphate content were determined in hindlimb skeletal muscle at baseline, during ischemia, and upon reperfusion. Four experimental groups (N = 7 in each group) were studied: control animals underwent aortic clamping and declamping; hypothermia animals underwent topical cooling of hindlimbs prior to aortic clamping, with muscle temperatures maintained between 5 and 15 degrees C during ischemia; sham animals underwent midline laparotomy only; and hypothermia-sham animals underwent cooling and midline laparotomy only. During ischemia, resting Em (-mV) was significantly depolarized (P < 0.05 versus baseline) in control (74.9 +/- 0.8 from 91.0 +/- 0.1), hypothermia (64.4 +/- 1.1 from 90.9 +/- 0.3), and hypothermia-sham (67.2 +/- 1.4 from 90.9 +/- 0.4) animals. Upon reperfusion, resting Em remained depolarized in control animals (74.7 +/- 1.6), while repolarization occurred in hypothermia (88.8 +/- 1.1) and hypothermia-sham (90.7 +/- 0.3) animals.(ABSTRACT TRUNCATED AT 250 WORDS)