In vivo evidence against a role for adenosine in the exercise pressor reflex in humans

The pressor response to exercise is of great importance in both physiology and pathophysiology. Whether endogenous adenosine is a trigger for this reflex remains controversial. Muscle interstitial adenosine concentration can be determined by microdialysis. However, there are indications that local muscle cell damage by the microdialysis probe confounds these measurements in exercising muscle. Therefore, we used the nucleoside uptake inhibitor dipyridamole as pharmacological tool to bypass this confounding. We used microdialysis probes to measure endogenous adenosine in forearm skeletal muscle of healthy volunteers during two cycles of 15 min of intermittent isometric handgripping. During the second contraction, dipyridamole (12 μg·min−1·dl forearm−1) was administered into the brachial artery. Dipyridamole potentiated the exercise-induced increase in dialysate adenosine from 0.30 ± 0.08 to 0.48 ± 0.10 μmol/l (n = 9, P < 0.05), but it did not potentiate the exercise-induced increase in blood pressure. A tim...