Proposed molecular mechanisms of H₂O₂-evoked vasoconstriction, based on the present study.

H₂O₂ may induce both vasodilation and vasoconstriction, depending on the applied H₂O₂ concentration, vessel type, species and experimental protocol (e.g. exposure time). Our data imply that H₂O₂ 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 Ca²⁺ sensitivity of the vascular smooth muscle in skeletal muscle arterioles of the rat (DAG: diacylglycerol).