H<sub>2</sub>O<sub>2</sub> increases the Ca<sup>2+</sup> sensitivity of force production in vascular smooth muscle cells.

<p>The changes in intracellular Ca<sup>2+</sup> levels and arteriolar diameters were studied in skeletal muscle arterioles under control conditions (panel A; n = 5 arterioles from 3 different animals), or after treatment with norepinephrine (panel B; n = 5 arterioles from 3 different animals), or by addition of the TXA2 receptor agonist U46619 (0.1 nM–10 µM; panel C; n = 5 arterioles from 4 different animals). Experiments were also performed in the presence of H<sub>2</sub>O<sub>2</sub> together with Src kinase inhibitor, (Src inhibitor-1, 5 µM n = 4 arterioles from 3 different animals, 20-min preincubation; panel D). Asterisks denote significant differences from the initial values.</p>