title: Unaltered catabolism of desialylated low-density lipoprotein in the pig and in cultured rat hepatocytes.
abstract: Removal of the terminal sialic acid residues from many serum glycoproteins results in exposure of their penultimate galactose residues and rapid clearance from circulation by the liver. Low-density lipoprotein is a glycoprotein containing 21 galactose and 9 sialic acid residues per particle. Studies in this laboratory and others have shown that both the liver and extrahepatic tissues contribute to the degradation of low-density lipoprotein. This study was undertaken to determine whether desialylation of pig low-density lipoprotein alters its removal from circulation. Low-density lipoprotein was incubated at 37 degrees C with an agarose-bound neuraminidase, proteinase-free, from Clostridium perfringens. After 18 h at pH 5.0, 70% of the sialic acid residues were removed. The desialylated 131I-labelled and native 125I-labelled low-density lipoproteins were simultaneously injected into a pig, and their disappearance from plasma was followed for 96 h. The turnovers of the two were identical. In contrast, neuraminidase-treated fetuin was cleared about 200-fold faster than native fetuin. Studies were also performed in cultured rat hepatocytes. Rates of degradation of native and neuraminidase-treated low-density lipoprotein were similar, whereas asialo-fetuin was degraded at six to ten times the rate of native fetuin. Thus desialylation does not appear to alter low-density-lipoprotein catabolism by hepatic or extrahepatic cells.
mesh_terms: D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D009439:Neuraminidase; D051381:Rats; D012794:Sialic Acids; D013552:Swine; D000509:alpha-Fetoproteins / Q000378:metabolism
chemical_list: D002241:Carbohydrates; D008077:Lipoproteins, LDL; D012794:Sialic Acids; D000509:alpha-Fetoproteins; D009439:Neuraminidase