Time-course of endothelial adaptation following acute and regular exercise.

Background: Regular exercise training has emerged as a powerful tool to improve endothelium-dependent vasorelaxation. However, little is known about the magnitude of change and the permanence of exercise-induced adaptations in endothelial function.

Design: Rats were randomized to either 6 weeks of regular exercise or one bout of exercise. Rats were then sacrificed 0, 6, 12, 24, 48, 96 or 192 h post-exercise, and vascular responsiveness to acetylcholine was determined.

Methods: Endothelium-dependent dilation was assessed by exposure to accumulating doses of acetylcholine in ring segments of the abdominal aorta from female Sprague-Dawley rats that either exercised regularly for 6 weeks or performed a single bout of exercise.

Results: A single exercise session improved endothelium-dependent vasodilatation for about 48 h. Six weeks of regular exercise induced a significantly larger improvement that lasted for about 192 h. Sensitivity to acetylcholine was twofold higher in chronically trained animals than in those exposed to a single bout of exercise. The decay after a single bout of exercise was about eightfold faster than that after 6 weeks of training.

Conclusion: The present data extend our concept of exercise-induced adaptation of endothelium-dependent vasodilatation in two regards: (1) a single bout of exercise improves endothelium-dependent dilation for about 2 days, with peak effect after 12-24 h; (2) regular exercise further improves adaptation and increases the sensitivity to acetylcholine approximately fourfold, which slowly returns to sedentary levels within a week of detraining.