The macromolecular particles of normal and regenerating rat liver.

The macromolecular particles, presumably nucleoprotein, from the cytoplasm of normal and regenerating rat liver have been studied in the analytical ultracentrifuge. Seven boundaries were seen, with sedimentation rates of 130, 107, 90, 72, 49, 38, and 27 S, corresponding to the microsomes and six macromolecular components. Regenerating liver showed a marked drop in the concentrations of the faster components accompanied by a rise in the two slowest components, especially during the period of most rapid cell division.