Abstract:

Objective To observe the effects of acute exhaustive running on rat cardiovascular ultrastructure and vessel function. Methods After adaptative running for 5 d, 24 male Wistar-Kyoto rats were assigned to sedentary control group (no more running, n=8), adaptative running group (adaptative running for another 5 d, n=8) and acute exhaustive running group (exhaustive running for another 5 d till refusal to running, n=8). After the end of running, the contraction and relaxation function of aortic vessels were assessed, and the ultrastructure of myocardium and aorta was examined under transmission electron microscope. Results Compared with sedentary control group and adaptative running group, the aortic contraction response to high potassium was not altered, while that to phenylephrine was significantly depressed in acute exhaustive running group (P<0.01). The endothelium-dependent vessel relaxation to acetylcholine was significantly enhanced in acute exhaustive running group (P<0.01), and was blocked by nitric oxide synthase inhibitor. Lysis of aortic endothelium, break of internal elastic lamina, infiltration of mononuclear macrophages around smooth muscles, degeneration in mitochondria and contraction band in myocardium in acute exhaustive running group were revealed by transmission electron microscopy. Conclusion Acute exhaustive running could lead to the impairment of vessel wall and myocardial mitochondria. The improvement in vessel relaxation and depression in contraction response may contribute to hypotension and sudden death after overexercise.

Key words: exhaustive running, vessel function, myocardium, ultrastructure, rat