Molecular Pharmacology, Vol 10, 398-405, Copyright © 1974 by the American Society for Pharmacology and Experimental Therapeutics

Phosphorylation of Rat Liver Nuclear Acidic Phosphoproteins after Administration of -1,2,3,4,5,6-Hexachlorocyclohexane in Vivo

¹ Department of Biochemistry, M. D. Anderson Hospital and Tumor Institute, and Graduate School of Biomedical Sciences, University of Texas, Houston, Texas 77025

-1,2,3,4,5,6-Hexachlorocyclohexane (-HCH) is known to induce mixed-function oxidases in rat liven endoplasmic reticulum and to stimulate liver cell proliferation. During the 12 hr after administration of -HCH the phosphorylation of nuclear acidic proteins in vivo increased to about twice the control level. Essentially all of the increased phosphorylation after -HCH in vivo involved preferential ³²P incorporation into fractions of phenol-solublel acidic chromatin proteins, resolved by polyacrylamide gel electrophoresis into proteins with estimated molecular weights of 15,000-25,000, 35,000-50,000, and 60,000-90,000. Although no qualitative changes in the electrophoretograms of phenol-soluble acidic chromatin proteins were observed, the incorportation of radioactive amino acids into the acidic protein fraction of rat liver nuclei in vivo increased 6 hr after -HCH, suggesting a change in turnover or an increased number of phosphate acceptor sites at the time of maximal phosphorylation of acidic nuclear phosphoproteins.

Note:
ACKNOWLEDGMENTS The authors are indebted to Mrs. Catherine Craddock and Mr. Augustus White for their excellent technical assistance.