Monitoring the exposure of rats to benzo[a]pyrene by the determination of mutagenic activity in excreta, chromosome aberrations and sister chromatid exchanges in peripheral blood cells, and DNA adducts in peripheral blood lymphocytes and liver.

The relative sensitivity of various methods suitable for monitoring the exposure to genotoxicants was studied in rats treated orally by gavage with benzo[a]pyrene (BP). The results were related to the occurrence of DNA adducts in liver. Male Wistar rats were treated once by gavage, BP doses ranging from 1 to 200 mg/kg body wt. The monitoring methods applied were: (i) mutagenicity in urine and extracts of faeces (Ames test, Salmonella typhimurium TA 100), (ii) chromosome aberrations (CA) and sister chromatid exchange (SCE) in peripheral blood lymphocytes (PBL), and (iii) DNA-adduct formation in PBL and liver (32P-postlabelling method). Mutagens in faeces and urine were detectable from dose levels of 1 and 10 mg/kg body wt respectively. Maximum mutagen levels were found in faeces (direct and indirect acting) collected 0-24 h after treatment and in urine (direct and indirect acting, glucuronidated and non-glucuronidated) collected 24-48 h after treatment. DNA-adduct formation was apparent in PBL at 10 mg (one spot) and 100 mg (two spots), and in liver at 100 mg/kg body wt (two spots). At the latter dose, the total BP-DNA adduct level in PBL was twice as high as in liver. The major adduct in PBL showed location and elution characteristics of the BP-adduct bound to N2 of doxyguanosine (BP-dG). None of the adducts in liver could be identified as BP-dG. A slight increase in SCE was seen in PBL only at 200 mg/kg body wt 6 h after treatment. CA did not increase at any of the dose levels used. Our results show that in vivo exposure of rats to BP can be detected by analysis of mutagenic activity in excreta and DNA-adducts in PBL. In contrast, measurement of CA and SCE in PBL appeared to be a rather insensitive method for detection of BP exposure.