Regulation of Skeletal Muscle Active Hyperemia: The Differential Role of Adenosine in Muscles of Varied Fiber Types.

摘要

Adenosine is one of several metabolites which have been proposed as metabolic regulators of the increased blood flow to exercising skeletal muscle. It has been shown that adenosine production with exercise varies in muscles having different oxidative capacities. Initial experiments suggested that adenosine may be produced under physiological conditions in oxidative muscles but not in glycolytic muscles. The purpose of these studies was to more clearly define the conditions under which a cause-and-effect relationship might exist between adenosine and skeletal muscle active hyperemia. In addition, these studies were designed to determine whether or not the intrinsic metabolic profile of the muscle involved, as indicated by fiber type, influences the extent to which adenosine modulates blood flow. Cat soleus (slow-twitch, oxidative) and cat gracilis (fast-twitch, glycolytic) muscles were stimulated to contract isometrically in the presence of adenosine deaminase (ADA), an enzyme which specifically degrades adenosine, or ADA which had been deactivated by boiling. Stimulation parameters were chosen to provide similar high and low blood flow responses in the two muscle types. ADA did not affect resting blood flow or vascular resistance. In the soleus muscle, ADA attenuated both the increase in blood flow and oxygen consumption, and the decrease in vascular resistance at the high level of muscle stimulation.