Acute exercise enhances receptor-mediated endothelium-dependent vasodilation by receptor upregulation

The effects of acute exercise on receptor-mediated endothelium-dependent vasodilation and its possible mechanisms were investigated in the presence of indomethacin. Male Wistar rats (16-20 weeks old) were divided into control and exercise groups. The exercise group ran on a drum exerciser until exhaustion, followed by immediate decapitation. Acetylcholine (ACh)- or clonidine (CLO)-induced vasodilating responses in thoracic aortae of the control and exercise groups were compared. Receptor-binding assays were performed to determine whether there were any upregulations of endothelial receptors after acute exercise. Our results indicated that acute exercise induced the following effects: (1) the dose-response curves of ACh and CLO shifted to the left; (2) the high-affinity M3 binding sites increased in number but not in affinity; (3) the alpha2 binding sites decreased in number but increased in affinity. We conclude that acute exercise enhances receptor-mediated vasodilation responses, at least in part, by regulating either endothelial receptor number or receptor affinity.