Modulation of the synthesis of apolipoproteins in rat hepatoma cells.
The present study was designed to investigate whether plasma lipoproteins and albumin can affect the basal synthetic rate of apolipoproteins in differentiated rat hepatoma cells (Fao) incubated in serum-free medium. The synthesis of apolipoproteins was measured by the incorporation of [35S]methionine into medium lipoproteins isolated by density gradient ultracentrifugation. Under all the experimental conditions used, Fao cells synthesized almost exclusively apolipoprotein E. When cells were incubated in the presence of 5-10% rat plasma the synthesis of apolipoprotein E increased 2-3-fold; lipoprotein-deficient serum had a negligible effect. Fatty acid-poor bovine serum albumin (BSA), which had been found to reduce very-low-density lipoprotein secretion in isolated rat hepatocytes, did not modify the synthesis of apolipoprotein E. When Fao cells were incubated in medium containing rat plasma lipoprotein fractions, the synthesis of apolipoprotein E increased. The d less than 1.090 g/ml plasma lipoprotein fraction had the major stimulatory effect. Increased apolipoprotein E synthesis was observed when cells were incubated in the presence of lipids extracted from rat plasma lipoproteins. These results suggest that the intracellular accumulation of lipoprotein-lipids plays an important role in regulating apolipoprotein E synthesis in Fao cells.
Pietrangelo
A
A
Istituti di Clinica Medica III, Università di Modena, Italy.
Tiozzo
R
R
Ghisellini
M
M
Cingi
M R
MR
Albertazzi
L
L
Ventura
E
E
Calandra
S
S
D000818:Animals; D001053:Apolipoproteins / Q000096:biosynthesis*; D003470:Culture Media; D004591:Electrophoresis, Polyacrylamide Gel; D008074:Lipoproteins / Q000494:pharmacology; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D051381:Rats; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000378:metabolism
D001053:Apolipoproteins; D003470:Culture Media; D008074:Lipoproteins; D012710:Serum Albumin, Bovine