L-Fucose-terminated glycoconjugates are recognized by pinocytosis receptors on macrophages.

125I-Labeled L-fucose-albumin complex and rat preputial beta-glucuronidase are rapidly cleared from plasma after intravenous infusion. L-Fucose-albumin retards the plasma clearance of beta-glucuronidase whereas D-fucose-albumin is inactive. In vitro, 125I-labeled L-fucose-albumin is taken up into rat or rabbit alveolar macrophages by receptor-mediated pinocytosis. Uptake (37 degrees C) is time-dependent, is saturable with increasing ligand concentration (Kuptake = 4.4 X 10(-8) M), and requires Ca2+. 125I-labeled D-fucose-albumin is poorly taken up. Binding (4 degrees C) is saturable and Ca2+ dependent. Binding and uptake are fully inhibited by yeast mannan. A series of neoglycoproteins, including L-fucose-albumin, were tested as inhibitors of uptake of 125I-labeled beta-glucuronidase into macrophages. The following order of potency was observed: L-Fuc = D-Man greater than GlcNAc approximately D-Glc greater than D-Xyl much greater than than D-Gal = L-Ara = D-Fuc. L-Fucose-terminated oligosaccharides coupled to bovine serum albumin also block 125I-labeled beta-glucuronidase uptake into macrophages.