Modulation of cardiac Na(+)-K+ pump current: role of protein and nonprotein sulfhydryl redox status.
Oxidant stress alters protein structure and function, possibly through the modification of the redox status of regulatory protein sulfhydryl groups. We used the sulfhydryl-blocking reagent p-chloromercuriphenylsulfonic acid (pCMPSA), applied selectively and independently to either the intracellular or extracellular environment, to study the relationship between blocking protein sulfhydryl groups and Na(+)-K+ pump current (i.p.). In guinea pig ventricular myocytes voltage clamped at -30 mV, extracellular pCMPSA (50, 100, and 400 microM) caused a concentration-dependent reduction in holding current. The selective intracellular administration of pCMPSA (100 microM) induced a similar inhibition of i.p., albeit over a longer time course. The inhibition of ip resulting from either the intracellular or extracellular application of pCMPSA (100 microM) was reversed, in part, by the extracellular application of dithiothreitol (3 mM). An intracellular oxidant stress was also imposed by using diethyl maleate to deplete the intracellular nonprotein sulfhydryl content [represented by reduced glutathione (GSH)]. In myocytes isolated from diethyl maleate-treated guinea pigs *860 mg/kg i.p., 30 min before study), intracellular GSH was depleted by 93% and i.p. was depressed by 38% at all membrane potentials tested. We propose that Na(+)-K+ pump function may be related to protein and nonprotein sulfhydryl status. Protein sulfhydryl oxidation and glutathione depletion may account, in part, for a depression in Na(+)-K+ pump activity during reperfusion-induced oxidant stress.
Haddock
P S
PS
Rayne Institute, St. Thomas' Hospital, London, United Kingdom.
Shattock
M J
MJ
Hearse
D J
DJ
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D004229:Dithiothreitol / Q000494:pharmacology; D004553:Electric Conductivity; D005978:Glutathione / Q000037:antagonists & inhibitors; D006168:Guinea Pigs; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010084:Oxidation-Reduction; D011188:Potassium / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000502:physiology*; D013438:Sulfhydryl Compounds / Q000378:metabolism*
D011506:Proteins; D013438:Sulfhydryl Compounds; D002731:4-Chloromercuribenzenesulfonate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D005978:Glutathione; D011188:Potassium; D004229:Dithiothreitol