Binding, uptake, and degradation of 125I-labelled high-density lipoproteins in isolated non-parenchymal rat liver cells.

Binding, uptake, and degradation of 125I-labelled HDL were measured in isolated rat non-parenchymal cells in vitro. The binding exhibited saturation kinetics and was inhibited to various degrees with other unlabelled lipoproteins such as VLDL, LDL, and HDL, but the uptake was not reduced by heat and formaldehyde-denatured albumin. The binding could be reduced by pronase treatment of the cells. Acetylated 125I-labelled HDL were more effectively taken up and degraded by non-parenchymal cells than unmodified 125I-labelled HDL. The Kupffer cells were able to take up two to three times as much HDL per cell as the endothelial cells. 125I-labelled HDL bind to the plasma cell membrane and can be dissociated by addition of unlabelled HDL. Relatively more labelled HDL dissociate at 4 degrees C than at 37 degrees C. The non-parenchymal cells also internalize 125I-labelled HDL at 37 degrees C, and the lysosomotropic drug chloroquine inhibits partly the degradation of accumulated 125I-labelled HDL.