Ouabain decreases sarco(endo)plasmic reticulum calcium ATPase activity in rat hearts by a process involving protein oxidation.
The effect of cardiac glycosides to increase cardiac inotropy by altering Ca(2+) cycling is well known but still poorly understood. The studies described in this report focus on defining the effects of ouabain signaling on sarcoplasmic reticulum Ca(2+)-ATPase function. Rat cardiac myocytes treated with 50 microM ouabain demonstrated substantial increases in systolic and diastolic Ca(2+) concentrations. The recovery time constant for the Ca(2+) transient, tau(Ca(2+)), was significantly prolonged by ouabain. Exposure to 10 microM H(2)O(2), which causes an increase in intracellular reactive oxygen species similar to that of 50 microM ouabain, caused a similar increase in tau(Ca(2+)). Concurrent exposure to 10 mM N-acetylcysteine or an aqueous extract from green tea (50 mg/ml) both prevented the increases in tau(Ca(2+)) as well as the changes in systolic or diastolic Ca(2+) concentrations. We also observed that 50 microM ouabain induced increases in developed pressure in addition to diastolic dysfunction in the isolated perfused rat heart. Coadministration of ouabain with N-acetylcysteine prevented these increases. Analysis of sarcoplasmic reticulum Ca(2+)-ATPase protein revealed increases in both the oxidation and nitrotyrosine content in the ouabain-treated hearts. Liquid chromatography-mass spectrometric analysis confirmed that the sarcoplasmic reticulum Ca(2+)-ATPase protein from ouabain-treated hearts had modifications consistent with oxidative and nitrosative stress. These data suggest that ouabain induces oxidative changes of the sarcoplasmic reticulum Ca(2+)-ATPase structure and function that may, in turn, produce some of the associated changes in Ca(2+) cycling and physiological function.
Kennedy
David J
DJ
Dept. of Medicine, Medical University of Ohio, Toledo, Ohio 43614-5089, USA.
Vetteth
Sandeep
S
Xie
Miaorong
M
Periyasamy
Sankaridrug M
SM
Xie
Zijian
Z
Han
Chi
C
Basrur
Venkatesha
V
Mutgi
Krishna
K
Fedorov
Vladimir
V
Malhotra
Deepak
D
Shapiro
Joseph I
JI
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology*; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*
D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D016877:Oxidants; D017382:Reactive Oxygen Species; D010042:Ouabain; D006861:Hydrogen Peroxide; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium; D000111:Acetylcysteine