Molecular Pharmacology, Vol 7, 191-198, Copyright © 1971 by the American Society for Pharmacology and Experimental Therapeutics

Effect of Administration of 3-Methylcholanthrene on the Salt-Extractable Chromatin Proteins of Rat Liver

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

It had previously been demonstrated than an increase in the efficiency of the template function of liver chromatin occurs after the administration of 3-methylcholanthrene (3-MC) to rats. The difference between control and 3-MC systems is eliminated by extraction of the chromatin with 2 M NaCl, a procedure which removes many of the nuclear proteins.

The profile of 2 M NaCl-extractable protein components of liver chromatin differs after treatment of rats with 3-MC, as determined by either disc electrophoretic or gel filtration techniques. The earliest change was seen 3-6 hr after drug treatment. The kinetics of incorporations of [¹⁴C] lysine into these components is also altered after drug treatment. After a 30-min pulse with the labeled precursor, a progressive increase in the specific activity of the 2 M NaCl-extractable proteins of liver chromatin was noted up to 24 hr after 3-MC treatment. At this time, a 100% increase over control levels was observed. Under the same conditions, the incorporation of [¹⁴C] L-tryptophan into the 2 M NaCl-extractable compo nents of liver was unaffectd by drug treatment. These changes may be related to the subsequent activation of the chromatin template for RNA synthesis.