The role of adenosine in prolonged vasodilation following flow-restricted exercise of canine skeletal muscle

Abstract

A period of prolonged vasodilation follows flow-restricted exercise of skeletal muscle. We tested the hypothesis that adenosine participates in mediating this vascular response. Vascularly isolated, anterior calf muscles of anesthetized dogs were stimulated to contract at a rate of 4 twitches/sec. Blood flow was held constant at 12.5 +/- 1.3 ml/min per 100 g which was about 14% of the expected free flow for this exercise level. Skeletal muscle tissue adenosine was measured with the an enzymatic, spectophotometric assay of trichloroacetic acid extracts of congruent to 50 mg biopsy samples. Tissue adenosine rose from 2.30 +/- 0.90 nmol/g in resting muscle to 22.5 +/- 5.8 nmol/g by the end of the 22-minute exercise. Following exercise, tissue adenosine fell toward its baseline value with a time course very similar to the early portion of the return of skeletal muscle vascular resistance to its control level. Thus, skeletal muscle adenosine content (1) increases to a sufficient magnitude and (2) falls with an appropriate time course to be at least partly responsible for the early portion of prolonged vasodilation seen after flow-restricted exercise of skeletal muscle.