GLUTATHIONE AND PROTEIN THIOL STATUS IN RENAL INJURY BY AMPHOTERICIN B (AMPH) IN RATS. † 2133

Abstract

The mechanisms responsible for AMPH-induced renal injury are not known. Because oxidant stresses appear to cause or exacerbate other examples of renal injury, we investigated oxidative mechanisms in AMPH nephrotoxicity. Fischer-344 (F344) rats are more suceptible to oxidant-induced injury than are Sprague-Dawley rats, and we found F344 rats to be slightly more sensitive to AMPH nephrotoxicity. Female F344 rats given single doses of 20 mg/kg of AMPH, i.p., developed elevated plasma BUN and Cr concentrations (59.7±0.6 and 1.03±0.05 mg/dl, respectively; vehicle-treated controls, 13.8±0.7 and 0.46±0.03) that peaked by 48 h, declining to baseline values by day 6 post dose. Tubular injury and progress through initial stages of tissue repair were observed by histology. Plasma and tissue levels of AMPH were measured by HPLC. Plasma concentrations showed an initial decline, with an apparent half-life of 23 h, through day 4, but no further decrease was observed through day 7 (peak 0.27; days 4-7 0.03 μg/ml). The concentrations of AMPH in renal and hepatic tissues were not closely correlated with plasma levels or tissue injury. Despite a 10-fold greater concentration of AMPH in liver (range of days 1-5: 16.9-59.4 μg/g tissue) than in kidney (1.11-3.53), plasma ALT activities did not increase. Biochemical and histologic evidence of recovery of renal injury was observed, even in animals with persistently high renal concentrations of AMPH. The redox status of renal proteins was assessed by fluorescence labeling with the thiol-specific reagent monobromobimane, followed by separation by SDS-PAGE. No substantive changes in total or in any individual protein thiol was observed, even in animals that showed marked renal damage. Further, biliary efflux of total glutathione did not increase as would be expected during an oxidant stress. Conclusions: 1) Hepatic vs renal injury do not correlate with tissue AMPH concentrations; 2) Recovery of renal function is observed despite the continued presence of AMPH; 4) Protein thiol status and biliary glutathione efflux do not support oxidant stress as the primary mechanism of AMPH nephrotoxicity.