Molecular Pharmacology, Vol 7, 183-190, Copyright © 1971 by the American Society for Pharmacology and Experimental Therapeutics

The Binding of 3-Methylcholanthrene to Macromolecular Components of Rat Liver Preparations

¹ Department of Pharmacology, Baylor College of Medicine, Houston, Texas 77025

If [¹⁴C] 3-Methylcholanthrene (3-MC) is incubated in vitro with the 9000 x g supernatant fraction of a rat liver homogenate in the presence of a pyridine nucleotide, and with the 100,000 x g supernatant liquid from the incubation mixture fractionated on Sephadex G-100, two ultraviolet-absorbing, radioactively labeled peaks are observed. Peak A is eluted in the void volume and has been shown to be at least partially composed of RNA. Peak B is partially excluded and is proteinaceous. Its formations is prevented by omission from the reaction mixture of microsomes or the pyridine nucleotide; the formation of peak A is unaffected by these procedures. The formations of peak B is greatly enhanced by treatment of the animals with 3-MC 24 hr before death, whereas the formations of peak A is only slightly stimulated. Under the same conditions some formation of peak A is observed in heart and kidney, but not in spleen; peak B formation, however, is completely absent in heart and spleen and very low in kidney. The relevance of the formation of these complexes is discussed with reference to enzyme induction by 3-MC in liver.