Rapid regulation of apolipoprotein A-I secretion in HepG2 cells by a factor associated with bovine high-density lipoproteins.
The effect of fetal bovine serum (FBS) on the secretion of apolipoprotein A-I (apo A-I) by HepG2 cells was studied. The cells incubated with FBS always secreted more apo A-I than the cells incubated with serum-free medium. The changes in the rate of apo A-I secretion were observed within 1 h after addition or depletion of serum. The high-density lipoproteins (HDL) or the lipoprotein-deficient serum (LPDS) obtained from FBS also stimulated apo A-I secretion rapidly to the same level as obtained with FBS. Addition of low-density lipoproteins did not have any effect. The rate of general protein synthesis was not affected by short-term incubations with or without serum or HDL. The rate of apolipoprotein E secretion by these cells did not change significantly, parallel to the changes in apo A-I secretion in the presence or absence of FBS. It is concluded that serum may have a factor that plays a specific role in the regulation of apo A-I secretion by the liver cells and this factor is associated with the HDL fraction.
Ranganathan
S
S
Atherosclerosis Research Unit, Mayo Clinic and Foundation, Rochester, MN 55905.
Kottke
B A
BA
D000818:Animals; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000096:biosynthesis / Q000378:metabolism*; D001057:Apolipoproteins E / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D002417:Cattle; D005312:Fetal Blood; D006358:Hot Temperature; D006801:Humans; D008075:Lipoproteins, HDL / Q000097:blood / Q000494:pharmacology*; D008077:Lipoproteins, LDL / Q000097:blood / Q000494:pharmacology; D008113:Liver Neoplasms / Q000378:metabolism*; D014357:Trypsin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D001057:Apolipoproteins E; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D014357:Trypsin