ENDOCYTIC PATHWAY OF HIGH-DENSITY LIPOPROTEIN VIA TRANS-GOLGI SYSTEM IN RAT RESIDENT PERITONEAL-MACROPHAGES

  • 1 September 1989
    • journal article
    • research article
    • Vol. 61  (3) , 270-277
Abstract
Interaction of high density lipoprotein (HDL) with rat resident peritoneal macrophages was investigated by morphological and biochemical approaches. Binding studies at 0.degree.C demonstrated saturable binding sites for 125I-HDL on the surface membrane. When cells were incubated with 125I-HDL at 37.degree.C, the cell-associated radioactivity increased with time, but intracellular degradation of HDL did not occur. Rather, the cell-associated 125I-HDL was released intact into the medium. Two morphological probes were employed to visualize the post-binding fate of HDL. Horseradish peroxidase and ferritin conjugates fo HDL showed specific bindings to the coated pits of the plasma membranes and were internalized and delivered through receptosomes to a trans-Golgi system. They were then resecreted as secretory visicles from the cells. Parallel experiments with transferrin-horseradish peroxidase peroxidase conjugates revelaed an endocytic pathway identical or very similar to that observed with HDL. These results provide evidence that internalization and subsequent nonlysosomal pathway via the trans-Golgi system are involved in receptor-mediated endocytosis of HDL by macrophages.

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