Metabolism and binding to cellular macromolecules of a series of hydrocarbons by mouse embryo cells in culture

A series of eight tritium‐labelled polycyclic hydrocarbons were incubated in the presence of monolayer cultures of primary mouse embryo cells, and the time‐course of their metabolism to water‐soluble derivatives was studied. All the hydrocarbons, both carcinogenic and non‐carcinogenic, were metabolized at approximately the same rate when a low concentration of the order of 0.05 μM was used. The binding of the various hydrocarbons to cellular DNA, RNA and protein was determined and a “binding index” calculated, i.e., the extent of reaction of the hydrocarbon with the particular macromolecule resulting from the metabolism of 1 mμmole of hydrocarbon per ml of medium to which the cells were exposed. While no very significant difference between the various hydrocarbons was found for the protein binding index, the DNA and RNA binding indices divided the compounds into two groups. One group with a high binding index consisted of potent carcinogens while the other group had much lower (one tenth) values for the binding index. With the exception of dibenz[a, h]anthracene, this latter group consisted of non‐carcinogens.