Objectives: This study examined vascular function and the adenosine system in skeletal muscle of patients diagnosed with essential hypertension (n = 10) and of normotensive (n = 11) patients, before and after aerobic training.

Methods: Before and after 8 weeks of aerobic training, the patients completed experiments in which leg blood flow was determined during infusion of adenosine, acetylcholine and during exercise (20 W); muscle interstitial fluid and femoral venous plasma were sampled via microdialysis probes during baseline conditions, exercise and adenosine infusion and resting muscle biopsies were obtained from muscle vastus lateralis.

Results: Before training, leg vascular conductance in response to arterial adenosine infusion was similar in the hypertensive and normotensive groups and the individual vascular response was positively correlated to that of both acetylcholine infusion (r ² = 0.66, P > 0.001) and exercise (r ² = 0.72, P < 0.001). Before training, interstitial adenosine concentrations during exercise and prostacyclin (PGI₂) concentrations after adenosine infusion were lower in the hypertensive than the normotensive group (P < 0.05). In the hypertensive group, training did not affect the vasodilatory response to arterially infused adenosine but increased the formation of interstitial adenosine and PGI₂ and lowered blood pressure. In the normotensive group, training resulted in lower (P < 0.05) leg vascular conductance in response to arterial adenosine infusion.

Conclusion: The present data suggest that essential hypertension is associated with a reduced capacity to form adenosine and PGI₂ at the skeletal muscle microcirculatory level, which is likely to contribute to the increased peripheral vascular resistance related to the disease. This impairment in vasodilator formation can be normalized by aerobic training.