Endocytosis of bovine lactoperoxidase by two carbohydrate-specific receptors in rat liver.
A perfused rat liver took up bovine lactoperoxidase (LPO) by a Ca2+-dependent, saturable process. This endocytosis was accomplished by both hepatocytes and Kupffer or other nonparenchymal cells (NPCs). The mediating receptors were the Gal/GalNAc lectin of hepatocytes and the Man/GlcNAc lectin of NPCs. Blocking either one of these receptors caused a large shift in distribution of accumulated LPO into the cell type whose receptor was left unblocked, but the extent of uptake was unaffected and the rate was only moderately reduced. Effective inhibition of overall uptake into the perfused organ required the presence of competitors for both receptors. Conversely, LPO was an effective competitor of other ligands (asialoorosomucoid or mannan) for either of the two receptors. The major clearance capacity for LPO was associated with hepatocytes which in suspension took it up by a process completely inhibitable by asialofetuin (ASF) and at a rate more than three times greater than for ASF. A faster cycling time for Gal/GalNAc receptors when bound to LPO is suggested. The glycoprotein selectively lost its affinity for Man/GlcNAc receptors when digested by endoglycosidase H (endo H), suggesting that LPO contains mannose-rich oligosaccharides.
Hildenbrandt
G R
GR
Aronson
N N
NN
D000818:Animals; D001212:Asialoglycoproteins; D001667:Binding, Competitive; D002118:Calcium / Q000502:physiology; D055598:Chemical Phenomena; D002621:Chemistry; D004533:Egtazic Acid / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects; D060748:Fetuins; D006596:Hexosaminidases; D066298:In Vitro Techniques; D007728:Kupffer Cells / Q000378:metabolism; D007784:Lactoperoxidase / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D037241:Mannose-Binding Lectins; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D010544:Peroxidases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011971:Receptors, Immunologic / Q000187:drug effects / Q000378:metabolism*; D000509:alpha-Fetoproteins / Q000494:pharmacology
D001212:Asialoglycoproteins; D060748:Fetuins; D037241:Mannose-Binding Lectins; D011971:Receptors, Immunologic; D000509:alpha-Fetoproteins; C017029:asialofetuin; C037045:galactose-N-acetylgalactosamine receptor; C035313:mannose-N-acetylglucosamine receptor; D004533:Egtazic Acid; D007784:Lactoperoxidase; D010544:Peroxidases; D006596:Hexosaminidases; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D002118:Calcium