title: Apolipoprotein B synthesis in humans: liver synthesizes only apolipoprotein B-100.
abstract: Apolipoprotein (apo) B-100 and B-48 are prominent apolipoproteins in VLDL, IDL, and chylomicrons. Organ cultures of normal adult human liver were established to ascertain the form of apo B synthesized by hepatocytes in humans. Human liver was minced and incubated in 15 mL methionine-free RPMI-1640 medium with 10% dialyzed fetal calf serum plus 250 microCi 35S-methionine for eight hours at 37 degrees C. Lipoproteins secreted by the liver were isolated by ultracentrifugation and the content of newly synthesized apo B determined by quantitation of radioactivity in the apoB-100 and apoB-48 bands after separation by 3% NaDodSO4 gel electrophoresis. In the eight-hour period, 2.5% to 3.2% of added 35S-methionine was secreted in TCA-precipitable protein of which 0.34% was apo B. Ninety-nine percent of the apo B in VLDL, IDL, and LDL was in the apo B-100 electrophoretic band. No significant radioactivity was detected in the apo B-48 electrophoretic band. Eighty-nine percent of the total radioactivity of apo B-100 was in VLDL with 3% and 8% in IDL and LDL, respectively. These results establish that adult human liver in organ culture synthesizes apo B-100 but not apo B-48.
mesh_terms: D000328:Adult; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000096:biosynthesis*; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007120:Immunochemistry; D008074:Lipoproteins / Q000096:biosynthesis / Q000145:classification; D008099:Liver / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D009924:Organ Culture Techniques; D013462:Sulfur Radioisotopes; D014461:Ultracentrifugation
chemical_list: D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D008074:Lipoproteins; D013462:Sulfur Radioisotopes; D008715:Methionine