Hydrogen peroxide elicits constriction of skeletal muscle arterioles by activating the arachidonic acid pathway.

Abstract

The molecular mechanisms of the vasoconstrictor responses evoked by hydrogen peroxide (H2O2) have not been clearly elucidated in skeletal muscle arterioles. Changes in diameter of isolated, cannulated and pressurized gracilis muscle arterioles (GAs) of Wistar-Kyoto rats were determined under various test conditions. H2O2 (10-100 µM) evoked concentration-dependent constrictions in the GAs, which were inhibited by endothelium removal, or by antagonists of phospholipase A (PLA; 100 µM 7,7-dimethyl-(5Z,8Z)-eicosadienoic acid), protein kinase C (PKC; 10 µM chelerythrine), phospholipase C (PLC; 10 µM U-73122), or Src family tyrosine kinase (Src kinase; 1 µM Src Inhibitor-1). Antagonists of thromboxane A2 (TXA2; 1 µM SQ-29548) or the non-specific cyclooxygenase (COX) inhibitor indomethacin (10 µM) converted constrictions to dilations. The COX-1 inhibitor (SC-560, 1 µM) demonstrated a greater reduction in constriction and conversion to dilation than that of COX-2 (celecoxib, 3 µM). H2O2 did not elicit significant changes in arteriolar Ca(2+) levels measured with Fura-2. These data suggest that H2O2 activates the endothelial Src kinase/PLC/PKC/PLA pathway, ultimately leading to the synthesis and release of TXA2 by COX-1, thereby increasing the Ca(2+) sensitivity of the vascular smooth muscle cells and eliciting constriction in rat skeletal muscle arterioles.