Plasma Clearance of Glycoproteins with Terminal Mannose and N - Acetylglucosamine by Liver Non - Parenchymal Cells STUDIES WITH , B - GLUCURONIDASE , N - ACETYL - fl - D - GLUCOSAMINIDASE , RIBONUCLEASE B AND AGALACTO - OROSOMUCOID

Glycoproteins having mannose and/or N-acetylglucosamine in the terminal non-reducing position [Stockert, Morell & Scheinberg (1976) Biochem. Biophys. Res. Commun. 68, 988-993], and various lysosomal enzymes [Stahl, Schlesinger, Rodman & Doebber (1976) Nature (London) 264, 86-88] are rapidly cleared from plasma by the liver after intravenous administration. A liver cell-separation technique was used to determine the cellular localization of '25I-labelled f,-glucuronidase, ribonuclease B, agalacto-orosomucoid and asialo-orosomucoid. On a specific radioactivity basis, all ligands except 1251-labelled asialo-orosomucoid were enriched in the non-parenchymal cell fraction. Isolated cells, fixed and stained for .8-glucuronidase or N-acetyl-fi-D-glucosaminidase activity after intravenous injection of the enzymes, showed enrichment in the non-parenchymal cell fraction (probably Kupffer cells). After uptake by the non-parenchymal cells, liver lysosomal 8-glucuronidase and N-acetyl-fl-D-glucosaminidase showed degradation halftimes of 2.2 and 0.4 days respectively.