Exercise Training-Enhanced, Endothelium-Dependent Dilation Mediated by Altered Regulation of BKCa Channels in Collateral-Dependent Porcine Coronary Arterioles

Microcirculation (Impact Factor: 2.57). 02/2013; 20(2). DOI: 10.1111/micc.12016


Test the hypothesis that exercise training increases the contribution of BKCa channels to endothelium‐mediated dilation in coronary arterioles from collateral‐dependent myocardial regions of chronically occluded pig hearts and may function downstream of H2O2. Methods
An ameroid constrictor was placed around the proximal left circumflex coronary artery to induce gradual occlusion in Yucatan miniature swine. Eight weeks postoperatively, pigs were randomly assigned to sedentary or exercise training (treadmill; 14 week) regimens. ResultsExercise training significantly enhanced bradykinin‐mediated dilation in collateral‐dependent arterioles (~125 μm diameter) compared with sedentary pigs. The BKCa‐channel blocker, iberiotoxin alone or in combination with the H2O2 scavenger, polyethylene glycol catalase, reversed exercise training‐enhanced dilation in collateral‐dependent arterioles. Iberiotoxin‐sensitive whole‐cell K+ currents (i.e., BKCa‐channel currents) were not different between smooth muscle cells of nonoccluded and collateral‐dependent arterioles of sedentary and exercise trained groups. Conclusions
These data provide evidence that BKCa‐channel activity contributes to exercise training‐enhanced endothelium‐dependent dilation in collateral‐dependent coronary arterioles despite no change in smooth muscle BKCa‐channel current. Taken together, our findings suggest that a component of the bradykinin signaling pathway, which stimulates BKCa channels, is enhanced by exercise training in collateral‐dependent arterioles and suggest a potential role for H2O2 as the mediator.

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