Premium
Exercise Training‐Enhanced, Endothelium‐Dependent Dilation Mediated by Altered Regulation of BK Ca Channels in Collateral‐Dependent Porcine Coronary Arterioles
Author(s) -
Xie Wei,
Parker Janet L.,
Heaps Cristine L.
Publication year - 2013
Publication title -
microcirculation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.793
H-Index - 83
eISSN - 1549-8719
pISSN - 1073-9688
DOI - 10.1111/micc.12016
Subject(s) - bradykinin , iberiotoxin , cardiology , medicine , endothelium , vascular smooth muscle , endocrinology , chemistry , vasodilation , smooth muscle , receptor
Objective Test the hypothesis that exercise training increases the contribution of BK Ca channels to endothelium‐mediated dilation in coronary arterioles from collateral‐dependent myocardial regions of chronically occluded pig hearts and may function downstream of H 2 O 2 . 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. Results Exercise training significantly enhanced bradykinin‐mediated dilation in collateral‐dependent arterioles (~125 μm diameter) compared with sedentary pigs. The BK Ca ‐channel blocker, iberiotoxin alone or in combination with the H 2 O 2 scavenger, polyethylene glycol catalase, reversed exercise training‐enhanced dilation in collateral‐dependent arterioles. Iberiotoxin‐sensitive whole‐cell K + currents (i.e., BK Ca ‐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 BK Ca ‐channel activity contributes to exercise training‐enhanced endothelium‐dependent dilation in collateral‐dependent coronary arterioles despite no change in smooth muscle BK Ca ‐channel current. Taken together, our findings suggest that a component of the bradykinin signaling pathway, which stimulates BK Ca channels, is enhanced by exercise training in collateral‐dependent arterioles and suggest a potential role for H 2 O 2 as the mediator.