Effect of 3-methylcholanthrene on the protein composition of heterogeneous nuclear ribonucleoprotein particles in developing rat liver.

Nine-day-old rats were treated with a single 100 mg/kg body weight intraperitoneal dose of 3-methylcholanthrene (3-MC). 24, 48, 72 and 120 h later the protein composition of the heterogeneous nuclear ribonucleoprotein particles derived from the liver was analysed. The analysis was performed by urea-sodium dodecyl sulphate polyacrylamide gel electrophoresis. The protein composition of the hnRNP particles was compared to that derived from control animals of similar ages. The 35 000-Mr polypeptide which is normally absent found in the hnRNP particles of the young rats prior to the 11th day of life appears on the 10th day after 24 h 3-MC exposition. In addition, the minor polypeptide components of the particles were also found in higher quantity. The polypeptide pattern of the hnRNP particles derived from treated animals resembled those of the older animals but not those of controls of similar ages. Thus, the apparent accelerating effect of 3-MC on the liver development is also valid at the level of hnRNP particles.