Apolipoprotein E (apo E) is a major plasma apolipoprotein found in both very low density and high density (HDL) lipoproteins. Apo E appears to be an important components of the reverse cholesterol transport system that delivers cholesterol from peripheral tissues to the liver for metabolism. Recent evidence indicated that apo E is synthesized in peripheral tissues as well as in the liver. The purpose of the present research is to determine the significance of peripheral apo E synthesis as it relates to reverse cholesterol transport and atherosclerosis. Toward this end, five specific questions have been identified. First, in which peripheral tissues is apo E made? These experiments will employ short-term organ-culture with radiolabeled amino acid and specific immunoprecipitation to identify newly synthesized apo E. Second, how much apo E is made in peripheral tissues as compared to the liver? These experiments will use a cDNA clone to apo E to determine the absolute apo E mRNA content in the liver and peripheral tissues. Third, which cells in peripheral tissues make apo E? These experiments will use a cDNA clone to apo E as a hisotlogical reagent for in situ hybridization to identify cells which contain apo E mRNA. Fourth, is apo E synthesis in peripheral cells regulated in the same fashion as in the liver? These experiments involve an analysis of apo E mRNA via S1 nuclease unapping, northern gel analysis, and primer extension procedures. Fifth, how are peripheral and hepatic apo E synthesis related to diet-induced changes in plasma lipoportiens and atherosclerosis. The experiments described above will be carried out with tissues from animals that are part of a long term study by other investigators on diet and atherosclerosis. As a result it will be possible to correlate the findings on peripheral apo E with diet-induced changes in lipoproteins and vascular disease. the long range goal of th is work is to elluciadate the functional nature of peripheral apo E as it relates to reverse cholesterol transport and atherosclerosis.
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