EFFECTS OF AGING AND EXERCISE ON FUNCTION OF SKELETAL MUSCLE ARTERIOLES

Abstract

Aging reduces in skeletal muscle blood flow capacity. This decrease in flow capacity may be due, in part, to decreased endothelium-dependent vasodilation of the skeletal muscle resistance vasculature. Experimental evidence indicates that age-related loss of endothelial function in the skeletal muscle resistance vasculature is attenuated by exercise training. We have used aged Fischer 344 rats to study endothelium-dependent function of skeletal muscle arterioles isolated from the soleus and gastrocnemius muscles. Endothelium-mediated vasodilation to acetylcholine is reduced in arterioles from soleus but not gastrocnemius muscle of aged rats. Flow-induced vasodilation is reduced with age in arterioles from both soleus and gastrocnemius muscles. Blockade of endothelial nitric oxide synthase indicates that the age-related reduction of acetylcholine- and flow-induced vasodilation in soleus muscle results from a reduction in nitric oxide mediated dilation. The impairment of flow-induced vasodilation in gastrocnemius muscle arterioles does not occur because of a diminution in a nitroxidergic mechanism. In contrast, exercise training ameliorates endothelial responsiveness to flow and acetylcholine in arterioles from both soleus and gastrocnemius muscles. Training restores dilation to flow and acetylcholine through enhancement of a nitric oxide mechanism in both soleus and gastrocnemius muscle arterioles. Thus, our current data indicate that aging-induced impairment of endothelial function is muscle specific. In contrast, exercise training restores endothelial function through augmentation of nitric oxide function in arterioles from both soleus and gastrocnemius muscles.