Role of Oxidative Stress in Ischemia–Reperfusion-Induced Changes in Na +,K + -ATPase Isoform Expression in Rat Heart

Abstract

The aim of this study was to assess whether depression of cardiac Na⁺,K⁺-ATPase activity during ischemia/reperfusion (I/R) is associated with alterations in Na⁺,K⁺-ATPase isoforms, and if oxidative stress participates in these I/R-induced changes. Na⁺,K⁺-ATPase α₁, α₂, α₃, β₁, β₂, and β₃ isoform contents were measured in isolated rat hearts subjected to I/R (30 min of global ischemia followed by 60 min of reperfusion) in the presence or absence of superoxide dismutase plus catalase (SOD+CAT). Effects of oxidative stress on Na⁺,K⁺-ATPase isoforms were also examined by perfusing the hearts for 20 min with 300 μM hydrogen peroxide or 2 mM xanthine plus 0.03 U/ml xanthine oxidase (XXO). I/R significantly reduced the protein levels of all α and β isoforms. Treatment of I/R hearts with SOD+CAT preserved the levels of α₂, α₃, β₁, β₂, and β₃ isoforms, but not that of the α₁ isoform. Perfusion of hearts with hydrogen peroxide and XXO depressed all Na⁺,K⁺-ATPase α and β isoforms, except for α₁. These results indicate that the I/R-induced decrease in Na⁺,K⁺-ATPase may be due to changes in Na⁺,K⁺-ATPase isoform expression and that oxidative stress plays a role in this alteration. Antioxidant treatment attenuated the I/R-induced changes in expression of all isoforms except α₁, which appears to be more resistant to oxidative stress. Antioxid. Redox Signal. 6, 914–923.