Fat-storing (Ito) cells of rat liver synthesize and secrete apolipoproteins: comparison with hepatocytes.
Fat-storing cells of the liver store most of the vitamin A of the body. Vitamin A is present in a few large fat droplets within the cell. The aim of our study was to investigate apolipoprotein biosynthesis in isolated fat-storing cells from rat liver during the time in culture. Isolated rat hepatocytes were studied for comparison. Proteins were biosynthetically labeled and further identified by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Apoproteins in culture supernatants were identified by density gradient ultracentrifugation and by one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of aliquots of the gradient. Rat plasma was processed in the same way and used for comparison. Fat-storing cells synthesized and secreted apoprotein E, apoprotein A-I, apoprotein A-IV, and low amounts of apoprotein C. The synthesis of these proteins increased during the culture time, reaching a maximum at the fifth day after isolation. The proteins were identified mostly as apoproteins of high-density lipoprotein. Hepatocytes synthesized and secreted apoproteins of all classes of lipoproteins. The distribution of high-density lipoprotein apoproteins was similar to that of fat-storing cells but hepatocytes produced larger amounts of the apoproteins.
Ramadori
G
G
Department of Internal Medicine, University of Mainz, Federal Republic of Germany.
Rieder
H
H
Theiss
F
F
Meyer zum Büschenfelde
K H
KH
D000818:Animals; D001053:Apolipoproteins / Q000032:analysis / Q000096:biosynthesis*; D002469:Cell Separation; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D050356:Lipid Metabolism; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D011233:Precipitin Tests; D051381:Rats; D011914:Rats, Inbred BN
D001053:Apolipoproteins