Effect of dexamethasone on the synthesis of dolichol-linked saccharides and glycoproteins in hepatocytes prepared from control and inflamed rats

Hepatocytes were prepared from control and inflamed rats. The incorporation of 14Cmannose into protein was increased in inflamed compared with control hepatocytes. The incorporation of 14Cmannose into protein was also increased when the hepatocytes were cultured in presence of dexamethasone (1 microM), either from control or inflamed rats. At the same time the incorporation of 14Cmannose into dolichol phosphate mannose and dolichol-linked oligosaccharide was increased due to inflammation. The presence of dexamethasone in the hepatocyte culture caused an increased formation of these two products; in particular its effect on oligosaccharide lipid formation was very pronounced. The ratios of activities of formation of 14Cmannose-labelled oligosaccharide lipid in inflamed over control hepatocytes gradually decrease when increasing amounts of exogenous dolichol phosphate was added in cell homogenate assay mixture. These results suggest that the increase of oligosaccharide lipid formation in inflammation could be due to a higher concentration of endogenous dolichol phosphate, as was shown for dolichol phosphate mannose formation in inflammation Sarkar & Mookerjea (1984) Biochem. J. 219, 429-436. In contrast, the ratio of activities of 14Cmannose-labelled oligosaccharide lipid between dexamethasone-treated and untreated hepatocytes shows only a slight increase when increasing concentrations of exogenous dolichol phosphate were added to the assays. This suggests that the stimulation of dolichol pyrophosphate oligosaccharide synthesis observed in dexamethasone treatment is probably due to the higher level of enzymes involved in oligosaccharide synthesis rather than higher level of endogenous dolichol phosphate in these cells.