Impairment of cardiac contractility and sarcoplasmic reticulum Ca2+ ATPase activity by hypochlorous acid: reversal by dithiothreitol.
Isolated rat hearts perfused with 100 microM hypochlorous acid (HOCl), a powerful oxidant produced by activated neutrophils, exhibited progressive impairment of contractile performance suggestive of a cytosolic Ca2+ overload (increased left ventricular end-diastolic pressure, increased aortic root perfusion pressure, and depressed pulse pressure). Sarcoplasmic reticulum (SR) enriched microsomal preparations isolated from HOCl-perfused hearts showed a significant decline, when compared with control hearts, in both Ca2+ ATPase activity (123 +/- 40 vs. 473 +/- 46 nmol Pi.mg-1 protein.min-1) and Ca2+ uptake (12 +/- 5 vs. 46 +/- 4 nmol Ca2+.mg-1 protein.min-1). The sulfhydryl content in Ca2+ ATPase and other proteins, as determined by [14C]iodoacetamide binding, was also progressively depleted in HOCl-perfused hearts. Perfusion of the HOCl-treated hearts with dithiothreitol (DTT), a disulfide reducing agent, resulted in a time-dependent attenuation, and eventual partial reversal, of the dysfunction in both contractility and SR Ca2+ ATPase activity. Protein thiol levels were concomitantly restored to near control values. The data indicate that HOCl-induced contractile dysfunction in heart is related to the inactivation of the SR Ca2+ ATPase as a result of thiol oxidation and suggest that DTT is capable of reversing this dysfunction in situ by reducing the oxidized sulfhydryls in the Ca2+ ATPase.
Eley
D W
DW
Department of Physiology, Faculty of Medicine, University of Ottawa, Ont., Canada.
Eley
J M
JM
Korecky
B
B
Fliss
H
H
D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000187:drug effects* / Q000378:metabolism; D003864:Depression, Chemical; D004229:Dithiothreitol / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects / Q000502:physiology; D006997:Hypochlorous Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D011506:Proteins / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013438:Sulfhydryl Compounds / Q000378:metabolism
D011506:Proteins; D013438:Sulfhydryl Compounds; D006997:Hypochlorous Acid; D000252:Calcium-Transporting ATPases; D002118:Calcium; D004229:Dithiothreitol