Skeletal muscle HSP72 level during endurance training: influence of peripheral arterial insufficiency

Abstract.

Heat shock protein 72 (HSP72), the inducible isoform of the HSP70 family, is synthesized in exercised rat muscles and in the ischaemic heart. To determine the isolated and combined effects of chronic ischaemia and repeated exercise on skeletal muscle HSP72 expression, male Wistar rats were subjected to unilateral occlusion of the iliac artery. Beginning 1 week after ischaemia, half the rats were exercised on a motor-driven treadmill once a day, 5 days/week, the other half were restricted to cage activity. Rats were sacrificed after 2, 4, or 8 weeks of endurance training, together with the age-matched sedentary rats. Tissue samples were obtained from the plantaris and the red portion of the quadriceps of both hind-limbs. Endurance-trained rats displayed significantly increased HSP72 levels in skeletal muscles. Occlusion of iliac artery did not affect the HSP72 level in muscle from sedentary rats but enhanced that in the trained rats. Mitochondrial oxidative capacity, as assessed from cytochrome oxidase and citrate synthase activities, decreased during growth in sedentary animals, but was significantly improved by endurance training. Nevertheless, increased oxidative capacity induced by endurance training was partially prevented by arterial occlusion. It is concluded that both HSP72 levels and mitochondrial oxidative capacity are affected by ischaemia and training but these changes are not necessarily related. Whereas superimposition of chronic exercise on peripheral arterial insufficiency increased HSP72 levels, our results demonstrate that endurance training even for extended period of time is not effective for improving oxidative capacity of ischaemic muscle.