Decreased Arteriolar Sensitivity to Shear Stress in Adult Rats is Reversed by Chronic Exercise Activity

Abstract

Objective:We tested the hypothesis that the decline in endothelium-dependent arteriolar dilation in adult rats is reversed by chronic exercise activity. Methods:Rats were divided into young (8–10 weeks)-sedentary (SED_Y), adult (29–32 weeks)-sedentary (SED_A), and adult-exercised (EX_A, treadmill exercise for 18–20 weeks) groups. Responses of isolated arterioles (∼50 µm at 80 mm Hg) of gracilis muscle were assessed to increases in perfusate flow and vasoactive agents. Results:With no differences in basal tone, maximal flow-induced dilations were not different between arterioles of SED_Yand SED_Arats (71 ± 2 and 72 ± 2% of passive diameter, respectively), yet the sensitivity of arterioles to shear stress (WSS₅₀) was significantly less in SED_Athan in SED_Yrats (35 ± 4 vs. 23 ± 3 dyne/cm², respectively). In vessels of EX_Arats, maximal flow-induced dilation was significantly augmented (88 ± 2% of passive diameter) and WSS₅₀(15 ± 1 dyn/cm²) was significantly reduced. Dilation to acetylcholine was enhanced in arterioles of EX_A, whereas dilation to sodium nitroprusside was not different in vessels of the three groups. Conclusion:Chronic exercise activity reverses age related reduction in sensitivity of arterioles to increases in wall shear stress. Microcirculation(2002) 9,91–97. DOI: 10.1038/sj/mn/7800124

• age
• treadmill
• skeletal muscle
• acetylcholine
• vasodilation