Binding and degradation of heavy and light subfractions of low density lipoprotein by cultured fibroblasts and macrophages.

The heavy and light subfractions of low density lipoprotein (LDL) were bound to the same extent and with the same affinity by the LDL receptors of cultured human fibroblasts, both when assayed at 4 degrees C and when assayed at 37 degrees C. They were also degraded similarly by the low affinity, LDL-receptor-mediated pathway exhibited by normal human monocyte-derived macrophages maintained in medium containing whole serum. Neither of the subfractions was taken up by the 'scavenger' pathway in mouse peritoneal or human monocyte-derived macrophages. Assuming that the LDL particles were not altered during isolation, the results provide no evidence to suggest that the higher fractional catabolic rate of light LDL observed in vivo can be explained by any preferential catabolism through LDL-receptor-mediated pathways.