Detection of DNA-reactive metabolites in serum and their tissue distribution in mice exposed to multiple doses of carcinogen mixtures: role in human biomonitoring.
Our previous studies suggested that body fluids such as serum can serve as a novel surrogate for DNA-containing tissues to overcome the major limiting factor of tissue availability in human biomonitoring assessments. We have now examined the detectability of DNA-reactive metabolites (DRMs) in the serum and tissues of male C57BL/6 mice administered up to 10 i.p. injections on alternate days of individual polynuclear aromatic hydrocarbons (PAHs) or a mixture containing 0.01, 0.1, 1.0 and 5.0 mg/kg body wt each of benzo[a]pyrene (BP), cyclopenta[cd]pyrene (CPP) and benzo[k]fluoranthene (BF) in 200 microl sunflower oil. Four hours after the last dose, blood serum was separated and incubated with salmon testes DNA (st-DNA). 32P-Postlabeling of the st-DNA showed essentially the same adduct pattern as found in the tissue DNA, indicating that DRMs of the PAHs used were presumably sequestered and accumulated in the serum proteins. Serum DRMs were detectable at all doses tested following exposure to a mixture of BP, CPP and BF, with varying degrees of detection of the individual PAHs. At doses > or = 1 mg/kg, CPP was more potent than BP and BF in producing serum DRMs as well as tissue DNA adducts. At lower doses, however, BP was more potent. Serum DRMs were enhanced 7-20 times when the animals received 1 mg/kg each of these PAHs in the form of a mixture as compared with individual PAHs, however, tissue DNA adduction was enhanced to a lesser degree (1.5- to 2-fold). Results from these studies suggest that: (i) DNA adduction by a particular carcinogen can be significantly higher when administered in the form of a mixture than administered individually; (ii) DNA-reactive metabolites can be detected by 32P-postlabeling in the serum of animals treated with environmentally significant doses of an artificial carcinogen mixture. This approach has implications for human biomonitoring and offers an advantage because this obviates the need to acquire human tissue DNA, a major obstacle in population biomonitoring studies.