Partial characterization of the N‐linked oligosaccharides occurring on rat hepatocyte glycoproteins

Abstract

AbstractPrimary monolayers of isolated rat hepatocytes were cultured in the presence of [2‐3H]mannose and [1‐14C]fucose to label metabolically the carbohydrate portion of glycoproteins. Subsequently, glycopeptides were prepared by extensive pronase digestion in order that the relative occurrence of N‐linked oligosaccharides could be examined by lectin‐agarose affinity chromatography.The results indicate that isolated rat hepatocytes are able to synthesize many of the N‐linked oligosaccharides known to be present in whole‐rat‐liver tissue and in rat‐serum glycoproteins. Differences were noticed, however, in the relative occurrence of N‐linked glycans and their degree of galactosylation. Biantennary complex‐type glycans were predominant in isolated rat hepatocytes, whereas the majority of the N‐linked complex‐type glycans in rat‐liver tissue glycoproteins has been reported to be of the tetraantennary type. Furthermore, the degree of P‐galactosylation of the glycans of the hepatocytes appeared to be substantially lower than reported for the peripheral branches of liver tissue complex‐type glycans. However, most of the P‐linked Gal residues present appeared to be substituted by sialic acid.