Toxicity of Trp-P-2 to cultured human and rat keratinocytes

Keratinocytes cultured from human and rat epidermis exhibited strongly dive rgent sensitivities to toxicity from the heterocyclic amine food mutagen Tr p-P-2. To find a biochemical basis for this difference, the cultured cells were compared in their expression of phase 1 and 2 biotransformation activi ties, mutagenic activation and macromolecular adducts. The human acid early passage rat cells expressed similar levels of ethoxyresorufin O-deethylase and N-acetyl transferase activities, their microsomes were similarly activ e in inducing bacterial mutagenesis when incubated with Trp-P-2, and the ke ratinocytes accumulated similar levels of DNA adducts over a 4-day treatmen t period. However, the human cells expressed an order of magnitude higher c ytosolic glutathione S-transferase activity than the rat cells, likely prov iding enhanced protection. Late passage rat epidermal cells were insensitiv e to Trp-P-2 toxicity, attributable to their rapid loss of measured cytochr ome P450 activity. Rat esophageal and fore-stomach epithelial cells resembl ed late passage rat epidermal cells in their lack of sensitivity to Trp-P-2 toxicity and lack of P450 activity. Human esophageal epithelial cells expr essed substantial P450 activity but, in contrast to human epidermal cells, were sensitive to Trp-P-2 toxicity. Thus keratinocytes provide a valuable s ystem in which to examine the basis Tor species- and tissue-specific differ ences in toxicity from this carcinogenic heterocyclic amine. (C) 2000 Elsev ier Science Ireland Ltd. All rights reserved.