Hprt lymphocyte mutant frequency in relation to DNA adduct formation in rats fed the hepatocarcinogen 2-acetylaminofluorene

The lymphocyte hypoxanthine-guanine phosphoribosyltransferase (Hprt) assay is frequently used as a biomarker for the exposure of both humans and labor atory animals to potentially carcinogenic agents. To obtain information con cerning the sensitivity of the rat Hprt lymphocyte assay toward aromatic am ine carcinogens, male F344 rats were fed 0.02% 2-acetylaminofluorene (2-AAF ) for 1 month and then returned to control diet for 2 months. At 4, 27, 48, 62, and 90 days after the initiation of 2-AAF-feeding, the frequency of mu tants in the Hprt gene was determined. In addition, DNA was isolated from l iver nuclei, spleen lymphocytes, bone marrow, and thymus, and DNA adducts w ere analyzed by P-32-postlabeling. 2-AAF feeding resulted in a significant induction of 6-thioguanine-resistant T-lymphocytes and the mutant frequency continued to increase after the 2-AAF feeding was stopped. The same major DNA adduct, N-(deoxyguanosin-8-yl)-2-aminofluorene, was detected in liver, spleen lymphocytes, bone marrow, and thymus. DNA adduct levels were greates t in the tumor target tissue (liver) but occurred in all T-lymphocyte compa rtments, being highest in spleen lymphocytes. The DNA adduct levels were hi ghest at the end of the 1-month 2-AAF feeding period and decreased rapidly in all tissues. The data indicate that the Hprt lymphocyte mutagenesis assa y detects arylamine carcinogens, but with relatively low sensitivity. (C) 1 999 Published by Elsevier Science Ireland Ltd.