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Nuclear Uptake and Subsequent Nuclear Metabolism of Benzo(a)pyrene Complexed to Cytosolic Proteins¹

Department of Biochemistry, Vermont Regional Cancer Center, The University of Vermont College of Medicine, Burlington, Vermont 05405

The binding of [³H]benzo(a)pyrene to proteins of rat liver cytosol, the nuclear uptake of cytosolic protein-bound [³H]-benzo(a)pyrene, and the subsequent nuclear metabolism of the polycyclic hydrocarbon were investigated. The binding of [³H]benzo(a)pyrene to cytosol had a saturable high affinity component with a K_d of 2.54 nM and a capacity of 530 fmol/mg protein. Specific binding of [³H]benzo(a)pyrene to cytosol was also assayed using sucrose density gradient analysis. Nuclear uptake of protein-bound [³H]benzo(a)pyrene was demonstrated both directly and by sucrose density gradient analysis. The nuclear benzo(a)pyrene was readily converted to metabolites which were qualitatively and quantitatively no different from nuclear metabolites of exogenously (not protein associated) added [³H]benzo(a)pyrene.

¹ This work was supported by Grant CA 20711 from the National Cancer Institute.

² On sabbatical leave from the Department of Pharmacy, University of Sydney, Sydney, New South Wales, 2006, Australia.

³ To whom requests for reprints should be addressed.

Received 12/29/80. Accepted 7/30/81.