The nature of the deoxyribonucleosides involved in the binding of carcinogenic hydrocarbons to the DNA of mouse embryo cells.

The DNA of mouse embryo cells was specifically labelled in the purine moieties with (G(3)H)-deoxyadenosine or in the cytosine moieties with (5-(3)H)-deoxycytidine. These cells were then treated with 7-methylbenz (a) anthracene (7MBA) or benzo (a)-pyrene (B(a)P) and the DNA isolated, degraded and fractionated by LH20 Sephadex column chromatography. When the purines of the DNA were tritium-labelled, radioactive hydroccarbondeoxyribonucleoside products were obtained. No such products were found with deoxycytidine pre-labelled DNA. Contrary to an earlier suggestion, these results indicate that it is the purine moieties of DNA which react with the metabolically activated hydrocarbon derivative in vivo.