Metabolic studies in isolated rat liver cells: II. Biosynthesis of serum low density lipoproteins and its regulation

Dispersed rat liver cells were used for study of protein and serum lipoprotein synthesis. Cellular leucine incorporatein was tested in the presence of various cofactors, buffers and inhibitors.14C‐leucine was incorporated into cellular protein at an active rate for 1 hr. Incorporation was more rapid in the presence of succinate, MgCl2, phosphate and nicotinamide, but these cofactors were not absolutely required. The liver cells also incorporated labeled leucine into lower density lipoproteins (1DL) and released the newly labeled 1DL into the incubation medium. Puromycin strongly inhibited the production of cellular protein and 1DL. The mode of cellular regulation of 1DL synthesis was examined. The rate of 1DL production was selectively enhanced by short term alimentation with dietary triglyceride or by the addition of a mixture of lipogenic cofactors to incubated liver cells. The utility of isolated liver cells as a preparation for metabolic control studies is discussed.