Synthesis and secretion of lipoproteins by human hepatocytes in culture |
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Authors: | M E Bouma M Pessah G Renaud N Amit D Catala R Infante |
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Institution: | 1. INSERUM U.9, H?pital St-Antoine 184, rue du Fg St-Antoine, 75012, Paris, France
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Abstract: | Summary Confluent monolayers of normal human hepatocytes obtained by collagenase perfusion of liver pragments were incubated in a
serum-free medium. Intracellular apolipoproteins apo AI, apo C, apo B, and apo E were detected between Day 1 and Day 6 of
the culture by immunoenzymatic staining using polyclonal antibodies directed against these apoproteins and monoclonal antibodies
directed against both forms of apo B (B100 and B48). Translation of mRNA isolated from these hepatocytes in an acellular system
revealed that apo AI and apo E were synthesized as the precusor forms of mature plasma apo AI and apo E. Three lipoprotein
fractions corresponding to the density of very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density
lipoprotein (HDL) were isolated from the medium at Day 5 of culture and examined by electron microscopy after negative staining.
VLDL and LDL particles are similar in size and shape to plasma lipoproteins; spherical HDL are larger than normal plasma particles
isolated at the same density. Their protein represented 44, 19.5, and 36.5% respectively, of the total lipoprotein protein.
The secretion rate of VLDL protein corresponded to that measured in primary cultures of rat hepatocytes. After incorporation
of 3H]glycerol, more than 92% of the 3H]triglyceride secreted into the medium was recovered in the VLDL fraction. These results demonstrate that primary cultures
of normal human hepatocytes are able to synthesize and secrete lipoproteins and thus could be a useful model to study lipoprotein
metabolism in human liver. |
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Keywords: | lipoproteins synthesis secretion hepatocytes culture human |
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