The metabolism of acetonitrile to cyanide by isolated rat hepatocytes.
The metabolism of saturated nitriles, including acetonitrile, has been assumed to occur by a cytochrome P-450-dependent oxidation at the alpha-carbon, yielding a cyanohydrin intermediate which may spontaneously degrade to hydrogen cyanide and an aldehyde. However, results of studies in our laboratory suggest that formaldehyde is not a metabolite of acetonitrile. Since acetonitrile is structurally similar to iodomethane, a substrate for glutathione (GSH) S-transferases, we hypothesized that the metabolism of acetonitrile to cyanide might also occur by a nucleophilic substitution reaction involving GSH. The present studies were conducted to investigate these hypotheses and to further our study of the effects of acetone on acetonitrile metabolism. Female Sprague-Dawley rats were pretreated with buthionine sulfoximine BSO (4 mmol/kg ip, at -4 and -2 hr), cobalt heme (90 mumol/kg sc, at -48 hr), acetone (1960 mg/kg po, at -24 hr), or vehicle, and hepatocytes were isolated after collagenase perfusion of the liver. BSO reduced the cellular GSH content by greater than 80%, but did not appear to affect the metabolism of acetonitrile: the liberation of cyanide correlated with cytochrome P-450, and not GSH, concentrations. Cobalt heme depleted hepatocellular cytochrome P-450 (-45%) content, decreased cell yield and viability, and resulted in a marked reduction in the metabolism of acetonitrile to cyanide. Cobalt heme did not affect the recovery of sodium cyanide from hepatocyte suspensions. Pretreatment of rats with acetone resulted in a twofold increase in the metabolism of acetonitrile to cyanide. Addition of acetone in vitro inhibited acetonitrile metabolism, with an IC50 of 319 microM.(ABSTRACT TRUNCATED AT 250 WORDS)
D000096:Acetone / Q000494:pharmacology; D000097:Acetonitriles / Q000378:metabolism*; D000818:Animals; D019328:Buthionine Sulfoximine; D003486:Cyanides / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D005260:Female; D006454:Hemoglobins / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008717:Methionine Sulfoximine / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D000097:Acetonitriles; D003486:Cyanides; D006454:Hemoglobins; C007098:coboglobin; D000096:Acetone; D008717:Methionine Sulfoximine; D019328:Buthionine Sulfoximine; D003577:Cytochrome P-450 Enzyme System; C032159:acetonitrile