title: Effect of antioxidants on para-aminophenol-induced toxicity in LLC-PK1 cells.
abstract: The present studies were designed to investigate the susceptibility of LLC-PK1 cells to cytotoxicity induced by para-aminophenol (PAP) and the ability of antioxidants to prevent PAP-induced cytotoxicity. LLC-PK1 cells were incubated for 4 h with varying concentrations of PAP (0-0.2 mM). Incubation was continued for 20 h and viability was monitored at 24 h after initial exposure to PAP. For coincubation experiments, cells were incubated for 4 h with various antioxidants [including ascorbate, glutathione (GSH), butylated hydroxytoluene (BHT), beta-nicotinamide adenine dinucleotide (NADH), or beta-nicotinamide adenine dinucleotide phosphate (NADPH)] in the absence or presence of 0.1 mM PAP. For preincubation experiments, cells were incubated for 1 h with ascorbate, GSH or NADPH. Antioxidants were removed and cells were exposed to 0 or 0.1 mM PAP for 4 h. Viability was determined 24 h following PAP exposure. LLC-PK1 cells displayed a steep concentration-response relationship for PAP; 0.1 mM PAP caused approximately 50% loss of viability. Coincubation with ascorbate, GSH and NADPH was without effect on cell viability in the absence of PAP and attenuated PAP-induced losses in viability. In contrast, NADH was ineffective in preventing PAP-induced cytotoxicity. BHT alone produced a significant loss of cell viability and was ineffective in preventing PAP cytotoxicity. Inability of NADH to prevent PAP-induced cytotoxicity was related to rapid degradation of NADH in aqueous solution. Preincubation of cells with ascorbate or GSH but not NADPH was associated with attenuation of PAP-induced cytotoxicity. These data suggest that (1) PAP is cytotoxic to LLC-PK1 cells, (2) a portion of PAP cytotoxicity is due to nonenzymatic oxidation that occurs in the incubation medium, and (3) a portion of PAP cytotoxicity is due to enzymatic or nonenzymatic oxidation that occurs within cells.
authors.affiliation: Department of Pharmaceutical Sciences, University of the Science in Philadelphia, 600 South 43rd Street, Philadelphia, PA 19104-4495, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Hallman
authors.forename: R
authors.initials: R
authors.lastname: Tchao
authors.forename: J B
authors.initials: JB
authors.lastname: Tarloff
mesh_terms: D000627:Aminophenols / Q000633:toxicity*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002084:Butylated Hydroxytoluene / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000494:pharmacology; D018374:LLC-PK1 Cells / Q000187:drug effects*; D009243:NAD / Q000494:pharmacology; D009249:NADP / Q000494:pharmacology; D013552:Swine
chemical_list: D000627:Aminophenols; D000975:Antioxidants; D009243:NAD; D002084:Butylated Hydroxytoluene; D009249:NADP; D005978:Glutathione; C026729:4-aminophenol