Peroxynitrite inhibits amiloride-sensitive Na+ currents in Xenopus oocytes expressing alpha beta gamma-rENaC.
We examined the effect of peroxynitrite (ONOO-) on the cloned rat epithelial Na+ channel (alpha beta gamma-rENaC) expressed in Xenopus oocytes. 3-Morpholinosydnonimine (SIN-1) was used to concurrently generate nitric oxide (.NO) and superoxide (O2-.), which react to form ONOO-, a species known to promote protein nitration and oxidation. Under control conditions, oocytes displayed an amiloride-sensitive whole cell conductance of 7.4 +/- 2.8 (SE) microS. When incubated at 18 degrees C with SIN-1 (1 mM) for 2 h (final ONOO- concentration = 10 microM), the amiloride-sensitive conductance was reduced to 0.8 +/- 0.5 microS. To evaluate whether the observed inhibition was due to ONOO-, as opposed to .NO, we also exposed oocytes to SIN-1 in the presence of urate (500 microM), a scavenger of ONOO- and superoxide dismutase, which scavenges O2-., converting SIN-1 from an ONOO- to an .NO donor. Under these conditions, conductance values remained at control levels following SIN-1 treatment. Tetranitromethane, an agent that oxidizes sulfhydryl groups at pH 6, also inhibited the amiloride-sensitive conductance. These data suggest that oxidation of critical sulfhydryl groups within rENaC by ONOO- directly inhibits channel activity.
DuVall
M D
MD
Department of Anesthesiology, University of Alabama at Birmingham 35233, USA.
Zhu
S
S
Fuller
C M
CM
Matalon
S
S
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D004553:Electric Conductivity; D053503:Epithelial Sodium Channels; D005260:Female; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism / Q000494:pharmacology* / Q000502:physiology; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D016877:Oxidants / Q000378:metabolism / Q000494:pharmacology* / Q000502:physiology; D051381:Rats; D012964:Sodium / Q000502:physiology*; D015222:Sodium Channels / Q000378:metabolism*; D013774:Tetranitromethane / Q000494:pharmacology; D014982:Xenopus laevis
D053503:Epithelial Sodium Channels; D009566:Nitrates; D016877:Oxidants; D015222:Sodium Channels; C039642:peroxynitric acid; C002385:linsidomine; D000584:Amiloride; D012964:Sodium; D008981:Molsidomine; D013774:Tetranitromethane; D002118:Calcium