Influence of chronic aerobic exercise on microcirculatory flow and nitric oxide in humans.

In the present study we assessed the effect of physical training on Laser Doppler skin flux (LDF) and nitric oxide (NO) release, before and after 3 min of brachial artery occlusion. To this end we performed laser Doppler measurements and the venous plasma assay of nitrite/nitrate (NOx) on 10 sedentary healthy subjects and 10 endurance athletes. The sedentary control subjects had lower basal and post reperfusion levels of NOx as compared to athletes (mean +/- SE: 27.8 +/- 3.5 vs. 33.2 +/- 3.4, 48.6 +/- 7.9 vs. 60.1 +/- 10.1 micromol/L; p < 0.05). LDF at baseline was not significantly different in the two groups (157.5 +/- 7.9 and 176.64 +/- 26.7 PU for sedentary subjects and athletes, respectively) while post ischemic LDF was significantly lower in nonathletic subjects than in athletes (209.9 +/- 13 and 343.8 +/- 21.3 PU, p < 0.001). In both groups the hyperaemic stimulus significantly increased LDF and NOx levels (p < 0.01 and p < 0.05, respectively). The flow reserve, estimated as peak/basal LDF, was significantly lower in control subjects than in athletes (1.34 +/- 0.2 and 2.32 +/- 0.9, respectively, p < 0.01). In athletes, as opposed to sedentary subjects, a direct correlation was found between plasma NOx concentration and LDF both in basal conditions (r = 0.92; p < 0.001), and during hyperaemia (r = 0.84; p < 0.01). In conclusion, compared to sedentary subjects, athletes had an enhanced nitric oxide release. Hyperaemia increased LDF and nitric oxide levels both in sedentary subjects and in athletes.