Inhibition of heart sarcolemmal Ca(2+)-pump activity by oxygen free radicals.
Oxygen free radicals have been implicated as mediators of cellular injury in ischemia-reperfusion. Since intracellular Ca(2+)-overload has been considered to play a crucial role in ischemia-reperfusion injury, this study was undertaken to examine the effects of oxygen free radicals on Ca(2+)-stimulated Mg(2+)-dependent ATPase activities and ATP-dependent Ca2+ accumulation in rat cardiac sarcolemmal membranes in vitro. Isolated rat heart sarcolemmal membranes were incubated with xanthine (X) + xanthine oxidase (XO) and assayed for Ca(2+)-pump activities. X + XO inhibited the Ca(2+)-pump activities in a time-dependent manner; a significant inhibition of Ca(2+)-stimulated ATPase activity was seen after one min of incubation. Superoxide dismutase showed a protective effect on depression in Ca(2+)-pump activities due to X + XO. To understand the involvement of sulfhydryl groups changes in causing depression of Ca(2+)-pump activities, the effects of oxygen free radicals on heart sarcolemmal sulfhydryl groups were also investigated. Heart sarcolemmal sulfhydryl groups were decreased by X + XO in a time-dependent manner. Superoxide dismutase showed a protective effect on sulfhydryl group depression caused by X + XO. N-ethylmaleimide, a sulfhydryl reagent, showed inhibitory effect on Ca(2+)-pump activities both in a time-, and a dose-dependent manner; dithiothreitol and cysteine prevented changes in Ca(2+)-pump activities caused by N-ethylmaleimide. The inhibitory effect of X + XO on Ca(2+)-pump activities were also prevented by the addition of dithiothreitol or cysteine. A significant correlation between changes in sarcolemmal Ca(2+)-stimulated ATPase activity and sarcolemmal sulfhydryl groups was seen.(ABSTRACT TRUNCATED AT 250 WORDS)
Kaneko
M
M
Third Department of Internal Medicine, Hamamatsu University School of Medicine, Japan.
Hayashi
H
H
Kobayashi
A
A
Yamazaki
N
N
Dhalla
N S
NS
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D005260:Female; D005609:Free Radicals; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D012508:Sarcolemma / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism; D019820:Xanthine; D014969:Xanthine Oxidase / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
D005609:Free Radicals; D013438:Sulfhydryl Compounds; D014970:Xanthines; D019820:Xanthine; D000255:Adenosine Triphosphate; D014969:Xanthine Oxidase; D002118:Calcium