Proposed molecular mechanisms of H<sub>2</sub>O<sub>2</sub>-evoked vasoconstriction, based on the present study.

<p>H<sub>2</sub>O<sub>2</sub> may induce both vasodilation and vasoconstriction, depending on the applied H<sub>2</sub>O<sub>2</sub> concentration, vessel type, species and experimental protocol (<i>e.g.</i> exposure time). Our data imply that H<sub>2</sub>O<sub>2</sub> elicits vasoconstriction by activating Src kinase, which activates the phospholipase C (PLC), protein kinase (PKC), phospholipase A (PLA) and cyclooxygenase (COX) pathway, leading to the production of thromboxane A2 (TXA2), which increases the Ca<sup>2+</sup> sensitivity of the vascular smooth muscle in skeletal muscle arterioles of the rat (DAG: diacylglycerol).</p>