Effect of exercise training on metallothionein levels of hypertensive rats.
Because oxidative stress may be involved in arterial hypertension by affecting the balance between relaxing and contracting factors of vascular smooth muscle, the training-induced adaptation of antioxidant defenses could be implicated in the antihypertensive effect of chronic exercise. It has been suggested that metallothionein (MT), a metal-binding protein, plays an antioxidant role in mammals. The aim of this experiment was to study whether chronic exercise (swimming) influences both the development of arterial hypertension in spontaneously hypertensive rats (SHR) and the modification of MT levels. Male SHR and Wistar Kyoto (WKY) rats as control were trained to swim 1 h.d-1 5 d.wk-1 for 8 wk and sacrificed 72 h after the last exercise period. MT and total thiol levels were then measured. Exercise training 1) reduced systolic blood pressure and heart rate in both SHR WKY rats, and 2) was associated with a decrease in hepatic and cardiac MT levels; there was an increase in the aortic MT amounts in exercised SHR only. No modifications were noted in the gastrocnemius muscle or kidneys. In exercised animals, total thiols were lower in the liver but not in kidneys. Chronic exercise induced a reduction in arterial hypertension development in SHR rats and an adaptation of the MT levels in cardiac, hepatic, and aortic tissues. Further experiments are needed to pinpoint the role of the MT in these two cases in which oxidative stress occurs.