Biomarkers of Collecting Duct Injury in Han-Wistar and Sprague-Dawley Rats Treated with N-Phenylanthranilic Acid

Abstract

N-phenylanthranilic acid is a chloride channel blocker that causes renal papillary necrosis in rats. Studies were conducted in two strains of male rats to evaluate novel biomarkers of nephrotoxicity. Han-Wistar rats were given daily oral doses of 50, 350, or up to 700 mg/kg/day of NPAA, and Sprague-Dawley rats were given 50 or 400 mg/kg/day of NPAA. Rats were euthanized on days 8 and 15. The candidate kidney injury biomarkers renal papillary antigen-1 (RPA-1, for collecting duct injury), clusterin (for general kidney injury), α-glutathione-S-transferase (a proximal tubular marker), and µ-glutathione-S-transferase (a distal tubular marker) were measured in urine by enzyme immunoassay. Characteristic degeneration and necrosis of the collecting duct and renal papilla were observed in Han-Wistar rats at the high dose on day 8 and at the mid and high doses on day 15, and in Sprague-Dawley rats given the high dose on days 8 and 15. Increases in urinary RPA-1, and to a lesser extent urine clusterin, were generally associated with the presence of collecting duct injury and were more sensitive than BUN and serum creatinine. On the other hand, decreases in α-glutathione-S-transferase without proximal tubule lesions in both strains and decreases in µ-glutathione-S-transferase in Sprague-Dawley rats only were not associated with morphological proximal or distal tubule abnormalities, so both were of less utility. It was concluded that RPA-1 is a new biomarker with utility in the detection of collecting duct injury in papillary necrosis in male rats.