Whole-body heat shock protects the ischemic rat heart by stimulating mitochondria respiration

Whole-body heat shock (HS) leads to an enhancement of postischemic mechanical function and an improvement in glucose use by the rat heart. Here, we examine the effect of HS on isolated mitochondrial metabolism during reperfusion in the working rat heart. Rats were anesthetized, and their body temperature was raised to 41-42 degrees C for 15 min. Control rats were treated the same way but were not exposed to hyperthermia. Twenty-four hours after HS or sham treatment, rats were reanesthetized and the hearts were removed for perfusion with Krebs-Henseleit buffer, containing 11 mmol glucose/L and 1.2 mmol palmitate/L prebound to 3% albumin. Hearts were subjected to 25 min of global ischemia followed by 30 min of reperfusion. At the end of reperfusion, heart mitochondria were isolated using differential centrifugation and respiration measured in the presence of pyruvate, glutamate, or palmitoylcarnitine. Hearts subjected to HS showed an enhanced recovery of function, expressed as aortic flow, during the reperfusion period, compared with sham hearts. This improved functional status was associated with a significant increase in state 3 respiration in the presence of pyruvate, glutamate, or palmitoylcarnitine. These results show that HS offers protection against ischemic damage, and that a possible mechanism might be the enhanced myocardial metabolism of fuels.