Biomonitoring of nitropolynuclear aromatic hydrocarbons via protein and DNA adducts

Nitropolynuclear aromatic hydrocarbons (nitro-PAHs) are widely distributed in the environment. For several chemicals in this class of compounds, mutagenic activity in bacterial and mammalian systems and tumorigenic activity in laboratory animals have been clearly documented. Procedures for assessing the risk to humans from exposure to nitro-PAHs have not been clearly defined, despite the wide-spread occurrence of such agents in the environment and their possible involvement in the etiology of some human cancers. Several methods are available for determining exposure, uptake, and metabolic activation of genotoxic carcinogens in humans. DNA adducts currently are regarded as the most direct markers of genotoxicity. However, several proteins are equally capable of forming adducts with electrophiles derived from xenobiotics. We focused on developing methods to detect and quantify adducts of 1-nitropyrene and 1,6-dinitropyrene with proteins and with DNA. 1-Nitropyrene is the most abundant nitro-PAH in emissions from combustion sources such as diesel engines. Although 1,6-dinitropyrene is far more mutagenic and more tumorigenic than 1-nitropyrene, it is present in the environment at lower levels. Seeking a highly sensitive method, we have utilized the 32P-postlabeling technique to establish the pattern of the DNA adducts formed in rat tissues, as well as in peripheral blood lymphocytes, following administration of both 1-nitropyrene and 1,6-dinitropyrene. We also present results on hemoglobin and albumin adducts formed after administration of these nitro-PAHs. [3H]1-Nitropyrene was given to male or female Fischer-344 or Sprague-Dawley rats by gavage at five dose levels ranging from 0.1 to 1,000 micrograms/kg of body weight. This led to stable hemoglobin adducts, which accounted for 0.08% +/- 0.05% of the dose. The radioactivity associated with hemoglobin following administration of [3H]1-nitropyrene was cleared with a half-life of 13.6 days. This is faster than the clearance of unmodified erythrocytes in the rat (half-life of 30 days). Treating the hemoglobin with 1% hydrochloric acid in acetone, to precipitate the globin, released the radioactivity so that none remained bound to the globin. Rather, the radioactivity remained bound to the heme moiety. To obtain structural information about the heme adducts, we incubated [3H]1-nitrosopyrene and [3H]4,5-epoxy-4,5-dihydro-1-nitropyrene with rat hemoglobin. In each case, [3H] was bound mainly to globin and, to a lesser extent, to the heme moiety.(ABSTRACT TRUNCATED AT 400 WORDS)