[Low density lipoprotein metabolism in human fibroblast tissue cultures]

After the lipoproteins of low density /LDL/ were incubated at 37 degrees, they spontaneously aggregated with formation of larger particles, which were mainly absorbed by the cells of the fibroblast culture. The radioassay data showed that LDL was accumulated intracellularly. Endocytosis was not apparently the single mechanism responsible for metabolic turnover of the lipoproteins in the cells as evidenced by the low value of radioactivity of the LDL protein degradation products in the cells, as well as by alterations in the structure of the lipoproteins both absorbed on the fibroblast surface and occurring in the incubation medium.