The synthesis of glycosaminoglycans in isolated hepatocytes during experimental liver fibrogenesis.
During human and experimental liver fibrogenesis, the pattern of glycosaminoglycans in fibrotic liver matrix is greatly changed by severalfold increases of hyaluronic acid, chondroitin sulfate, and dermatan sulfate, respectively. The present study aimed to determine whether hepatocytes take part during fibrogenesis in the alteration of the glycosaminoglycan profile in liver matrix. Rats received thioacetamide orally for 2 and 10 weeks, respectively. After 10 weeks a typical micronodular cirrhosis had developed. Hepatocytes isolated at these time points were characterized by light and electron microscopy and incubated for up to 4 h in suspension cultures in [35S]-sulfate and [3H]-glucosamine containing medium to study the synthesis and intra-/extracellular distribution of total and specific types of glycosaminoglycans. A biphasic change of glycosaminoglycan synthesis in hepatocytes was found. After 2 weeks of TAA-treatment parenchymal cells synthesized about 25% more labeled glycosaminoglycans than control liver cells, but at 10 weeks the synthesis was reduced by more than 40%. Thus, between 2 and 10 weeks of TAA-treatment hepatocellular glycosaminoglycan synthesis decreased by more than 50%. The major portion of newly synthesized glycosaminoglycans was nitrous acid labile and, hence, identified as heparan sulfate. Its fractional synthesis decreased from 0.90 in control cells to 0.84 (2 weeks TAA) and 0.76 (10 weeks TAA), respectively. Thus, the absolute synthesis of heparan sulfate was reduced by 50% in hepatocytes from cirrhosis liver. Eighty to 90% of labeled glycosaminoglycans remained cell-associated. Hyaluronic acid was detected neither in normal hepatocytes nor in hepatocytes from injured liver. We conclude from these data that parenchymal liver cells will not contribute actively to the accumulation of galactosaminoglycans (chondroitin sulfate, dermatan sulfate) and hyaluronic acid in the extracellular matrix during fibrogenesis. The diminished rate of synthesis of heparan sulfate in hepatocytes from cirrhotic liver might explain its fractional decrease in cirrhotic liver matrix.
Meyer
D
D
Department of Clinical Chemistry, Philipps University, Marburg, FRG.
Zimmermann
T
T
Müller
D
D
Franke
H
H
Dargel
R
R
Gressner
A M
AM
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D006025:Glycosaminoglycans / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism / Q000473:pathology*; D008106:Liver Cirrhosis, Experimental / Q000139:chemically induced / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013853:Thioacetamide / Q000633:toxicity
D006025:Glycosaminoglycans; D013853:Thioacetamide