EN
The vasoconstrictor effect of hydrogen peroxide (H2O2) on isolated perfused rat kidney was investigated. H2O2 induced vasoconstriction in the isolated rat kidney in a concentration-dependent manner. The vasoconstrictor effects of H2O2 were completely inhibited by 1200 U/ml catalase. Endothelium-removal potentiated the renal response to H2O2. The H2O2 dose-response curve was not significantly modified by administration of the NO inhibitor L-NAME (10-4 mol/l), whereas it was increased by the non-specific inhibitor of K+-channels, tetraethylammonium (3·10-3 mol/l). Separately, removal of extracellular Ca2+, administration of a mixture of calcium desensitizing agents (nitroprusside, papaverine, and diazoxide), and administration of a protein kinase C (PKC) inhibitor (chelerythrine, 10-5 mol/l) each significantly attenuated the vasoconstrictor response to H2O2, which was virtually suppressed when they were performed together. The pressor response to H2O2 was not affected by: dimethyl sulfoxide (7·10-3 mol/l) plus mannitol (3·10-3 mol/l); intracellular Ca2+ chelation using BAPTA (10-5 mol/l); calcium store depletion after repeated doses of phenylephrine (10-5 g/g kidney); or the presence of indomethacin (10-5 mol/l), ODYA (2·10-6 mol/l) or genistein (10-5 mol/l). We conclude that the vasoconstrictor response to H2O2 in the rat renal vasculature comprises the following components: 1) extracellular calcium influx, 2) activation of PKC, and 3) stimulation of pathways leading to sensitization of contractile elements to calcium. Moreover, a reduced pressor responsiveness to H2O2 in female kidneys was observed.