Hydrogen peroxide-induced current in Xenopus oocytes: current characteristics similar to those induced by the removal of extracellular calcium

Abstract

The effects of hydrogen peroxide (H2O2) exposure on Xenopus oocytes were examined. An application of I muL of 10% H2O2 to oocytes voltage-clamped in I mL of Modified Barth Saline (MBS: final concentration of 0.01% H2O2) induced a transient ionic current. This H2O2-induced current, however, was not transient but long-lasting in a Ca2+-free medium. The H2O2-induced current was independent of increases in intracellular calcium. Intriguingly, the H2O2-induced current was similar in signature to one stimulated by the removal of extracellular calcium (Ca-o(2+)-inactivated current). Both currents (a) were inactivated by 1.5 mM LaCl3, GdCl3, CdCl2, NiCl2, CaCl2, or MgCl2, but not by LiCl or KCl, (b) exhibited reversal potential shifts to more positive values with increasing external NaCl, (c) showed linear voltage-current (I-VI) relationships, and (d) were reversibly inhibited by two chloride channel blockers, 200 muM 5-nitro-2-(3-phenylpropylamino)-benzoic acid and 250 muM niflumic acid. Additionally, H2O2 was still able to induce current in oocytes loaded with either catalase or N-acetyl-L-cysteine, H2O2 scavengers. These results imply that H2O2 induces this ionic current possibly through the activation of Ca-o(2+)-inactivated channels by an extracellular mechanism. (C) 2002 Elsevier Science Inc. All rights reserved.