Effects of sulphydryl reagents on the formation of the aniline metabolite 4-aminophenol and its sulphate and glucuronide conjugates in primary cultures of rat hepatocytes

Abstract

1. The effects of various sulphydryl-blocking reagents on aniline biotransformation and cytochrome P-450 levels were studied in cultured rat hepatocytes.

2. Exposure of aniline-metabolizing hepatocytes to p-chloro-mercuribenzoate (PCMB) or p-chloromercuribenzenesulphonic acid (PCMBS) resulted in decreased levels of cytochrome P-450, decreased glucuronidation of 4-aminophenol and increased levels of free 4-aminophenol.

3. Incubation of aniline-metabolizing hepatocytes with disulfiram resulted in decreased formation of 4-aminophenol, but this was not associated with impaired glucuronidation or cytochrome P-450 levels.

4. Exposure of aniline-metabolizing hepatocytes to mersalyl, 2,2′-dithiodipyridine (DTP), 6,6′-carboxydipyridine disulphide (CPDS) or N-ethylmaleimide did not affect the biotransformation of aniline or cytochrome P-450 levels.

5. Metyrapone prevented degradation of cytochrome P-450. Exposure of cells to SKF-525 A inhibited aniline biotransformation without altering cytochrome P-450 levels.

6. PCMB and PCMBS inhibited aniline metabolism, probably by binding to a cysteinyl-SH residue in cytochrome P-450 apoenzyme and ‘active sites’ of UDP-glucuronyl transferases. Disulfiram inhibited aniline biotransformation, probably indirectly by diminishing NADPH.