Interaction of free cholesterol and apoproteins of low and high density lipoproteins with isolated rabbit hepatocytes.

Primary cultures of rabbit hepatocytes were incubated with rabbit high density (HDL) and low density (LDL) lipoproteins in order to compare the surface trans- fer of free cholesterol with the uptake of apoproteins. Hepatocytes were maintained for various intervals with either LDL or HDL which contained both '251-labeled pro- tein and free (4-14C)cholesterol. After a 3-hr incubation with an LDL concentration equivalent to 25% of the normal rabbit serum level, the percentage of media I4C in hepatocytes was 2.3 times greater than the percentage of lz5I; cells that had been incubated with HDL showed an eight-fold selec- tivity for I4C. Although the influx of free cholesterol from HDL was greater than that from LDL, there was no difference between the uptake of LDL protein and of HDL protein. The degradation of lipoproteins labeled with (3H)- leucine or lZ5I was compared. Hepatocytes incubated with lipoproteins labeled with (4-14C)cholesterol showed a greater