Carcinogen-protein complexes in mammary gland after administration of 3-methylcholanthrene

Twenty-four hrs after i.p. administration of ³H-3-methylcholanthrene (³H-MCA) to 8–10 weeks old virgin or 14 days pregnant $\text{BALB}\text{c}$ mice, the macromolecules and ³H-hydrocarbon-protein complexes in their mammary cytosols were extensively resolved according to molecular size. The profiles of the macromolecules at both stages of mammary development were generally similar, and contained at least five families of molecular size of modes: > 300,000, 181,000, 88,000, 44,000 and 27,000 daltons. At least three species of ³H-hydrocarbon-protein complex were present. The principal complex had a modal molecular weight of 83,000, and the two minor species > 300,000 and 47,000. Only a small amount of complex similar to the principal species was produced $\text{in vitro}$ by incubation of ³H-MCA with cytosol at 1–4°, indicating that the carcinogen is probably metabolized prior to interaction $\text{in vivo}$ with its principal target protein.