Human and rat kidney cell metabolism of 2-acetylaminofluorene and benzo(a)pyrene

The metabolism and mutagenic activation of the model carcinogens benzo(a)pyrene [B(a)P] and 2-acetylaminofluorene (AAF) by human and rat kidney cells were measured. A slicing technique followed by enzyme digestion was utilized to obtain the kidney cells. Although levels of total metabolism of B(a)P by rat and human kidney cells were similar, analysis of specific metabolites of B(a)P indicated that species differences existed. Human kidney cells produced the organic-soluble metabolites B(a)P-9,10-diol, B(a)P-4,5-diol, B(a)P-7,8-diol, B(a)P-3,6-quinone, and B(a)P-9-phenol. Rat kidney cells produced organic-soluble B(a)P-pre-9,10-diols, B(a)P-9,10-diol, B(a)P-4,5-diol, and B(a)P-6,12-quinone. Both species produced sulfate and glucuronide conjugates of all products. For AAF, kidney cells from some human tissues produced up to four times the level of total metabolites compared to rat kidney cells. Organic-soluble metabolites were qualitatively similar between the species and consisted of 2-aminofluorene (AF), N-hydroxy-AAF and ring-hydroxylated products at the 1, 3, 5/9, 7, and 8 positions. Sulfate and glucuronide conjugates of these metabolites were also detected. Human interindividual variation with kidney cells was about 2.5-fold for total AAF metabolism and up to 6-fold for individual AAF metabolites. For B(a)P metabolism, human interindividual variation in total metabolism was low while for specific metabolites there was up to a 4-fold variation. Levels of AAF and AF cell-mediated Salmonella typhimurium mutagenesis were significantly higher with human cells as compared to rat kidney cells. It appears that the differences between human and rodent kidney cell metabolism of chemical carcinogens vary with the chemical class and understanding these differences will be necessary in the extrapolation of rodent carcinogenesis data to humans.