No abstract

The hepatoblastoma cell line HepG2 has been a matter of many investigations; most of them include biochemical studies of lipoprotein and other hepatic protein metabolism. However, the accurate cellular features of these cells have not been emphasized. We studied the cellular histologic, histochemical, and ultrastructural characteristics of this cell line. In addition, we investigated by immunoenzymatic methods the cellular biosynthesis of several proteins: apolipoproteins-AI, -B, -D, and -E, albumin, alpha-fetoprotein, transferrin, alpha-1-antitrypsin, C-reactive protein, fibronectin, and collagens I, III and IV. The rates of accumulation, in the medium of HepG2 cells, of albumin, alpha-1-antitrypsin, transferrin, and alpha-fetoprotein were 13.2 +/- 1.9; 4.9 +/- 1.5; 3.2 +/- 0.4; and 10.7 +/- 1.7 micrograms/10(6) cells/24 h, respectively. Our results show that HepG2 cells exhibited most cellular features of normal human hepatocytes. Bile canaliculi as well as Golgi apparatus complexes were particularly developed. Except for the C-reactive protein, HepG2 cells have all retained the ability to synthesize hepatic proteins but with some variable intensity from cell to cell. This hepatoblastoma cell line seems to represent a useful tool in the understanding of hepatic protein biosynthesis, particularly for the investigation on the secretory pathway of plasma proteins.

Abstract-Anderson's disease is a rare, hereditary hypocholesterolemic syndrome characterized by chronic diarrhea, steatorrhea, and failure to thrive associated with the absence of apo B48 -containing lipoproteins. To further define the molecular basis of the disease, we studied 8 affected subjects in 7 unrelated families of North African origin after treatment with a low-fat diet. Lipid loading of intestinal biopsies persisted, but the pattern and extent of loading was variable among the patients. Electron microscopy showed lipoprotein-like particles in membrane-bound compartments, the densities (0.65 to 7.5 particles/ 2 ) and the mean diameters (169 to 580 nm) of which were, in general, significantly larger than in a normal fed subject (0.66 particles/ 2 , 209 nm mean diameter). There were also large lipid particles having diameters up to 7043 nm (average diameters from 368 to 2127 nm) that were not surrounded by a membrane. Rarely, lipoprotein-like particles 50 to 150 nm in diameter were observed in the intercellular spaces. Intestinal organ culture showed that apo B and apo AIV were synthesized with apparently normal molecular weights and that small amounts were secreted in lipid-bound forms (density Ͻ1.006 g/mL). Normal microsomal triglyceride transfer protein (MTP) and activity were also detected in intestinal biopsies. Segregation analyses of 4 families excluded, as a cause of the disease, significant regions of the genome surrounding the genes for apo AI, AIV, B, CI, CII, CIII, and E, as were the genes encoding 3 proteins involved in intracellular lipid transport, MTP, and fatty acid binding proteins 1 and 2. The results suggest that a factor other than apoproteins and MTP are important for human intestinal chylomicron assembly and secretion.

No abstract

No abstract