A Study of High Density Lipoprotein (HDL) Receptors Expressed on a Human Hepatoma Cell Line Mahlavu
The journal of Japan Atherosclerosis Society(1990)
摘要
High density lipoproteins (HDL) may play an important role in removing cholesterol from peripheral tissue and deliver it to the liver, acting as a shuttle in reverse cholesterol transport. The mode of interaction between the liver and HDL, however, has not yet been clarified.We investigated catabolism of human HDL in a human hepatoma cell line Mahlavu. The binding of 125I-Iabeled HDL at 4°C was time-dependent and reached completion within 2hr. The observed binding rates of 125I-labeled HDL at 4°C and the uptake and degradation at 37°C indicated the presence of both specific and non-specific HDL binding sites. Non-specific binding occured in proportion to the concentration of 125I-Iabeled HDL. Specific binding of 125I-labeled HDL accounted for 60% (at 4°C) and 75% (at 37°C) of total binding capacity. The association and degradation of 125I-labeled HDL was inhibited by the addition of unlabeled HDL, but not LDL, suggesting HDL specificity. The lysosomal degradation of 125I-labeled HDL was time-dependent and inhibited only 10% and 20% by chloroquine at 50μM and 100μM concentrations, respectively. This finding suggested that HDL was metabolized through a non-lysosomal pathway.There was a marked difference in the degradation modes of 125I-labeled HDL between fibroblasts and Mahlavu cells. The degradation of 125I-labeled HDL by Mahlavu cells increased over time, while only a small portion of 125I-labeled HDL was degraded by fibroblasts. This data shows that hepatocytes such as Mahlavu cells have HDL receptors which are considerably different from those of fibroblasts. This cell line provides a good model for analyzing interactions between HDL and hepatocytes in humans.
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关键词
high density lipoprotein,hdl,receptors
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