O2 metabolite-mediated injury in perfused kidneys is reflected by consumption of DMTU and glutathione

Abstract

The contribution of toxic oxygen (O2) metabolites to ischemic renal injury is unclear because they have not been added directly to the kidney and few ways exist to effectively measure and assess the effect of these highly reactive products in biological systems. Our goal was to determine the effect of hydrogen peroxide (H2O2) or H2O2-derived products on renal function and to determine whether H2O2-mediated renal injury was reflected by consumption of dimethylthiourea (DMTU) (an exogenous O2 metabolic scavenger), depletion of renal cortical total glutathione (an endogenous O2 metabolite scavenger), and/or adenosine triphosphate (ATP). We found that addition of glucose oxidase (GO) or H2O2 to isolated perfused rat kidneys caused injury that was manifested by decreases in glomerular filtration rate, perfusion flow rate, and sodium reabsorption and that was prevented by addition of catalase (CAT) (but not inactivated CAT) or large doses of DMTU (15 mM), but not urea (15 mM). To further ascertain if the protective effect of DMTU was due to reacting with a scavenging H2O2, we conducted parallel experiments in which we measured the consumption of smaller doses of DMTU (1 mM) in kidneys perfused with GO or H2O2. We found that addition of increasing concentrations of H2O2 decreased DMTU concentration. Renal cortical total glutathione and ATP levels were also decreased by addition of GO or H2O2. In contrast to perfusion with GO or H2O2, perfusion with elastase or collagenase also caused renal injury and decreases in ATP but did not decrease DMTU concentration or tissue total glutathione. We conclude that H2O2 or H2O2-derived products are acutely toxic to the kidney and that decreases in perfusate DMTU concentration and tissue total glutathione, but not tissue ATP, may be useful for specifically assessing the presence and/or toxicity of H2O2 in renal and other biological systems.