H2O2 Is the Transferrable Factor Mediating Flow-Induced Dilation in Human Coronary Arterioles
Rationale: Endothelial derived hydrogen peroxide (H2O2) is a necessary component of the pathway regulating flow-mediated dilation (FMD) in human coronary arterioles (HCAs). However, H2O2 has never been shown to be the endothelium-dependent transferrable hyperpolarization factor (EDHF) in response to shear stress.
Objective: We examined the hypothesis that H2O2 serves as the EDHF in HCAs to shear stress.
Methods and Results: Two HCAs were cannulated in series (a donor intact vessel upstream and endothelium-denuded detector vessel downstream). Diameter changes to flow were examined in the absence and presence of polyethylene glycol catalase (PEG-CAT). The open state probability of large conductance Ca2+-activated K+ (BKCa) channels in smooth muscle cells downstream from the perfusate from an endothelium-intact arteriole was examined by patch clamping. In some experiments, a cyanogen bromide–activated resin column bound with CAT was used to remove H2O2 from the donor vessel. When flow proceeds from donor to detector, both vessels dilate (donor: 68±7%; detector: 45±11%). With flow in the opposite direction, only the donor vessel dilates. PEG-CAT contacting only the detector vessel blocked FMD in that vessel (6±4%) but not in donor vessel (61±13%). Paxilline inhibited dilation of endothelium-denuded HCAs to H2O2. Effluent from donor vessels elicited K+ channel opening in an iberiotoxin- or PEG-CAT–sensitive fashion in cell-attached patches but had little effect on channel opening on inside-out patches. Vasodilation of detector vessels was diminished when exposed to effluent from CAT-column.
Conclusions: Flow induced endothelial production of H2O2, which acts as the transferrable EDHF activating BKCa channels on the smooth muscle cells.
- Received May 7, 2010.
- Revision received December 20, 2010.
- Accepted December 29, 2010.
- © 2011 American Heart Association, Inc.