ascorbic-acid and acivicin

p-Aminophenol (PAP) produces nephrotoxicity in rats through a mechanism presumably involving oxidation and conjugation with glutathione (GSH). Recently it was found that PAP also causes nephrotoxicity in mice as evidenced by elevated blood urea nitrogen (BUN) and serum creatinine levels. The objective of this study was to further investigate the mechanism and elucidate the role of GSH in PAP-induced nephrotoxicity in the mouse. Male C57BL/6 mice injected i.p. with various doses of PAP were sacrificed at 12 hr for measurement of BUN and serum creatinine levels and determination of the extent of renal cortical nonprotein sulfhydryl (NPSH) and GSH depletion. PAP depleted renal cortical NPSH content in a dose- and time-dependent manner. Depletion of NPSH in mouse kidney did not occur at PAP doses below 600 mg/kg. Buthionine sulfoximine, an inhibitor of GSH synthesis, decreased nephrotoxicity. Ascorbate, a reducing agent, prevented PAP-induced nephrotoxicity and attenuated renal cortical NPSH depletion. However, acivicin and aminooxyacetic acid, inhibitors of gamma-glutamyltranspeptidase and beta-lyase, respectively, did not prevent toxicity in the mouse. Piperonyl butoxide, an inhibitor of cytochrome P-450 enzymes, enhanced nephrotoxicity and renal cysteine depletion but not GSH depletion. The results suggest that PAP-induced nephrotoxicity in the mouse may involve oxidation and formation of a GSH conjugate.

Topics: Aminophenols; Animals; Ascorbic Acid; Buthionine Sulfoximine; Dose-Response Relationship, Drug; Glutathione; Isoxazoles; Kidney; Male; Mice; Mice, Inbred C57BL; Oxidation-Reduction; Piperonyl Butoxide

A halogenated derivative of 4-aminophenol, 4-amino-2, 6-dichlorophenol (ADCP), is a potent nephrotoxicant and a weak hepatotoxicant in Fischer 344 rats. Although the mechanism of ADCP nephrotoxicity is unknown, ADCP could undergo oxidation to a reactive intermediate, such as a 4-amino-2,6-dichlorophenoxy radical or 2,6-dichloro-1,4-benzoquinoneimine, which can generate additional free radicals and/or covalently bind to cellular proteins. The toxic process might also be mediated by glutathione (GSH) conjugates of ADCP, as suggested for the mechanism of 4-aminophenol nephrotoxicity. In this study, the effects of modulators of oxidation and GSH conjugation-related metabolism or transport on ADCP-induced nephrotoxicity were examined. In one set of experiments, male Fischer 344 rats (four/group) were intraperitoneally (ip) administered ADCP (0.38 mmol/kg) only or coadministered an antioxidant, ascorbic acid (1.14 mmol/kg, ip) with ADCP. Administration of ascorbic acid markedly reduced both functional nephrotoxicity and morphological changes induced by ADCP. Administration of a gamma-glutamyltransferase (GGT) inhibitor, l-(alphaS, 5S)-alpha-amino-3-chloro-4,5-dihydroxy-5-isoxazoleacetic acid (10 mg/kg, ip), or a cysteine conjugate beta-lyase inhibitor, aminooxyacetic acid (0.5 mmol/kg, ip), 1 hr before ADCP (0.38 mmol/kg) challenge partially protected rats against ADCP nephrotoxicity. In contrast, administration of an organic anion transport inhibitor, probenecid (140 mg/kg, ip), 30 min before ADCP had little effect on ADCP nephrotoxicity. The GSH depletor, buthionine sulfoximine (890 mg/kg, ip), was given 2 hr prior to ADCP and only minimal protection was noted. In addition, the nonprotein sulfhydryl (NPSH) contents in renal cortex and liver were determined at 2 hr following the administration of ADCP only or ascorbic acid/ADCP. Ascorbic acid afforded complete prevention of the depletion of NPSH in the kidney and liver caused by ADCP administration and also prevented the elevation of renal glutathione disulfide content induced by ADCP. The results indicate that oxidation of ADCP appears to be essential to ADCP nephrotoxicity and that GSH or GSH-derived conjugates of ADCP may be partly responsible for the nephrotoxic effects of ADCP via a GGT-mediated mechanism.

Topics: Aminooxyacetic Acid; Animals; Antioxidants; Ascorbic Acid; Buthionine Sulfoximine; Chlorophenols; Drug Interactions; Enzyme Inhibitors; gamma-Glutamyltransferase; Glutathione; Injections, Intraperitoneal; Isoxazoles; Kidney Cortex; Liver; Male; Probenecid; Rats; Rats, Inbred F344; Sulfhydryl Compounds

The nephrotoxicity of 4-amino-3-S-glutathionylphenol (PAP-GSH), a known metabolite of 4-amino-phenol (PAP), was determined in male Fischer 344 rats. Administration of a single dose of 40 or 60 mumol kg-1 caused a marked elevation in blood urea nitrogen and an increase in the urinary excretion of glucose, protein and gamma-glutamyltransferase (GGT). These changes were associated with histological alterations in the proximal tubule, where at the lower dose the lesion was restricted to the S3 region of the proximal tubule in the medullary rays, while at the higher dose the lesion extended to affect the S3 region in both the medullary rays and the outer stripe of the outer medulla. Studies with [35S]-PAP-GSH at 40 mumol kg-1 showed selective retention of radioactivity in the kidney, relative to other organs 24 h after dosing and that some radioactivity was covalently bound to renal proteins. Pretreatment of animals with probenecid, an inhibitor of renal organic anion transport, or aminooxyacetic acid, an inhibitor of cysteine conjugate beta-lyase, had little or no effect on the toxicity. In contrast, pretreatment of animals with acivicin, an inhibitor of gamma-glutamyltransferase, or co-administration of PAP-GSH with ascorbic acid almost completely protected against the nephrotoxicity. This protection was associated with a decreased concentration of radioactivity from [35S]-PAP-GSH in the kidneys and a decrease in the amount covalently bound to renal protein. Thus, the nephrotoxicity of PAP-GSH may be mediated by oxidation and further processing of the glutathione conjugate via gamma-glutamyltransferase.

Topics: Aminooxyacetic Acid; Animals; Ascorbic Acid; Blood Urea Nitrogen; gamma-Glutamyltransferase; Glutathione; Glycosuria; Ion Transport; Isoxazoles; Kidney; Lyases; Male; Oxidation-Reduction; Phenols; Probenecid; Proteinuria; Rats; Rats, Inbred F344; Sulfur Radioisotopes

4-Aminophenol (p-aminophenol, PAP) causes selective necrosis to the pars recta of the proximal tubule in Fischer 344 rats. The basis for this selective toxicity is not known but PAP can undergo oxidation in a variety of systems to form the 4-aminophenoxy free radical. Oxidation or disproportionation of this radical will form 1,4-benzoquinoneimine which can covalently bind to cellular macromolecules. We have recently reported that a glutathione conjugate of PAP, 4-amino-3-S-glutathionylphenol, is more toxic to the kidney than the parent compound itself. In this study we have examined the distribution and covalent binding of radiolabel from 4-[ring 3H]-aminophenol in the plasma, kidney and liver of rats 24 h after dosing and related these findings to the extent of nephrotoxicity. In addition, we have examined the effect of ascorbic acid which will slow the oxidation of PAP; acivicin, an inhibitor of gamma-glutamyltransferase and hence the processing of glutathione-derived conjugates; and probenecid, an inhibitor of organic anion transport on the nephrotoxicity produced by PAP. Administration of a single dose of PAP at 458 or 687 mumol kg-1 produced a dose-related alteration in renal function within 24 h which was associated with proximal tubular necrosis. The lesion at the lower dose was restricted to the S3 proximal tubules in the medullary rays, while at the higher dose it additionally affected the S3 tubules in the pars recta region of the cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Aminophenols; Animals; Antimetabolites; Ascorbic Acid; Isoxazoles; Kidney; Kidney Diseases; Kidney Function Tests; Liver; Male; Probenecid; Rats; Rats, Inbred F344

Topics: Animals; Ascorbic Acid; Blood Urea Nitrogen; Chloranil; Drug Synergism; gamma-Glutamyltransferase; Glutathione; Isoxazoles; Kidney; Rats

Administration of either 2,5-dichloro-3-(glutathion-S-yl)-1, 4-benzoquinone (DC-[GSyl]BQ) or 2,5,6-trichloro-3-(glutathion-S-yl)-1,4-benzoquinone (TC-[GSyl]BQ) to male Sprague-Dawley rats caused dose-dependent (50-200 mumol/kg; iv) renal proximal tubular necrosis, as evidenced by elevations in blood urea nitrogen (BUN), and in the urinary excretion of lactate dehydrogenase (LDH), gamma-glutamyl transpeptidase (gamma-GT) and glucose. Renal proximal tubular necrosis was also confirmed by histological examination of kidney slices prepared from DC-(GSyl)BQ- and TC-(GSyl)BQ-treated animals. Administration of the corresponding hydroquinone conjugates (DC-[GSyl]HQ and TC-[GSyl]HQ), prepared by reducing the quinones with a threefold molar excess of ascorbic acid, resulted in a substantial increase in nephrotoxicity. Moreover, in contrast to other glutathione (GSH)-conjugated hydroquinones, the nephrotoxicity of both DC-(GSyl)HQ and TC-(GSyl)HQ was potentiated when rats were pretreated with AT-125, an irreversible inhibitor of gamma-GT. Neither the quinone-GSH nor the hydroquinone-GSH conjugates caused any effect on liver histology or serum glutamate-pyruvate transaminase levels. The results suggest that coadministration of ascorbic acid with DC-(GSyl)BQ or TC-(GSyl)BQ decreases their interactions with extrarenal nucleophiles, including plasma proteins, and thus increases the concentration of the conjugates delivered to the kidney, and hence toxicity. Furthermore the ability of AT-125 to potentiate the nephrotoxicity of DC-(GSyl)HQ and TC-(GSyl)HQ suggests that metabolism of these conjugates by gamma-GT constitutes a detoxication reaction.

Topics: Animals; Ascorbic Acid; Chloranil; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Drug Synergism; Electrochemistry; gamma-Glutamyltransferase; Glutathione; Isoxazoles; Kidney Cortex; Kidney Diseases; Kidney Tubular Necrosis, Acute; Male; Oxidation-Reduction; Rats; Rats, Inbred Strains