Sulfotransferase-Mediated Chlorination of 1-Hydroxymethylpyrene to a Mutagen Capable of Penetrating Indicator Cells
Environmental Health Perspectives
Methylated polycyclic aromatic hydrocarbons are common in the human environment. Many of them are stronger carcinogens than their purely aromatic congeners. They may be metabolized to benzylic alcohols. We report here on biochemical and toxicological characteristics of 1-hydroxymethylpyrene (HMP), a typical representative of this class of compounds. Rat liver cytosol, fortified with 3'-phosphoadenosine-5'-phosphosulfate, converted HMP into its sulfate ester (HMPS). HMPS bound covalently to
... covalently to isolated DNA. In physiological buffer at 370C, HMPS had a half-life of 2 min, the major decomposition product being HMP. Thus, cyclic activation is possible. When Cl-anions were present at physiological concentrations, an additional reaction product of HMPS, 1-chloromethylpyrene (CIMP), could be identified on the basis of its chromatographic properties and its mass spectrum, using the authentic standard for comparison. CIMP was shorter-lived in buffer than HMPS. CIMP reacted with DNA, the adduct pattern in the 32P-postlabeling analysis being similar, or identical, to that of HMPS. CIMP proved to be a very potent mutagen in Salmonella typhimurium, whereas HMPS, and HMP in the presence of a sulfateconjugating system, showed strong mutagenicity only when Cl-or Br-ions were present in the exposure buffer. It is concluded that HMPS is capable of reacting with DNA, but is hampered in its distribution by membrane barriers. Strikingly, a CIMP intermediate is produced, which can act as a transport form to overcome membrane barriers. Among 10 investigated tissues, HMP-activating sulfotransferases were found at appreciable levels only in the liver, and there the activity in parenchymal cells exceeded that in Kupffer cells by a factor of -200. Distribution processes and their restrictions may, therefore, be important factors determining the toxicology of benzylic alcohols and other compounds activated through conjugation with sulfate.