Exercise Training Lowers Arterial Blood Pressure Independently of Pannexin-1 in Men with Essential Hypertension

Introduction: Regular exercise training reduces arterial blood pressure, but the underlying mechanisms are unclear. Here, we evaluated the potential involvement of pannexin 1, an ATP releasing channel, in the blood pressure-reducing effect of training. Methods: Middle-age men, 13 normotensive and 14 nonmedicated stage 1 hypertensive, completed 8 wk of intensive aerobic cycle training. Before and after training, blood pressure and changes in leg vascular conductance, induced by femoral arterial infusion of tyramine (induces endogenous noradrenaline release), acetylcholine, or sodium nitropmsside, were measured during control conditions and after acute pannexin 1 inhibition by probenecid. A skeletal muscle biopsy was obtained from the thigh, pre- and posttraining. Results: Exercise training reduced mean systolic and diastolic blood pressure by similar to 5 (P = 0.013) and 5 mm Hg (P < 0.001), respectively, in the hypertensive group only. The reduction in blood pressure was not related to changes in pannexin 1 function because mean arterial blood pressure and tyramine-induced vasoconstriction remain unaltered by pannexin 1 inhibition after training in both groups. After training, pannexin 1 inhibition enhanced leg vascular conductance in the nonno- and hypertensive groups at baseline (41.5%, P = 0.0036, and 37.7%, P = 0.024, respectively) and in response to sodium nitropmsside infusion (275%, P = 0.038, and 188%, P = 0.038, respectively). Training did not alter the pannexin 1 protein expression in skeletal muscle. Training enhanced the vasodilator response to acetylcholine infusion and increased the expression of microvascular function-relevant proteins. Conclusions: The exercise training-induced lowering of arterial blood pressure in nonmedicated hypertensive men does not involve an altered function of pannexin 1.