Increase in nitric oxide formation after chronic voluntary exercise in spontaneously hypertensive rats

The effect of chronic voluntary exercise on the plasma level of nitrate, a major stable metabolite of nitric oxide (NO) was studied in spontaneously hypertensive rats (SHR). Exercise consisted of spontaneous running in wheels for 3-35 days. Blood samples were collected after 3, 7, 14, 21 and 35 days of exercise and all samples were drawn after the running wheel had been locked during the preceding 12 h. The plasma nitrate level was significantly (P < 0.05) elevated in SHR after 35 days of exercise. Surprisingly after 7 days of exercise a significant (P < 0.001) decrease in the nitrate level in plasma was noted. Further research is needed to elucidate this biphasic change in nitrate seen in this study. The elevated level of plasma nitrate seen after 35 days of voluntary exercise was still present up to 36 h after termination of exercise. We conclude that exercise training in SHR elicits an enhanced formation of NO.