Abstract
A light microscopic and ultrastructural analysis of lectin receptors on parietal cells from human gastric mucosa was performed utilizing 12 biotinylated lectins in conjunction with an avidin-biotin-peroxidase complex. Peanut agglutinin conjugated directly to peroxidase was also used. Several fixatives and fixation regimens were evaluated for optimal preservation of parietal cell saccharide moieties. Formalin proved to be the most practical fixative for light microscopic studies. A periodate-lysine-paraformaldehyde (PLP) combination provided good preservation of lectin binding capacity but yielded relatively poor ultrastructure. Conversely, glutaraldehyde provided excellent preservation of ultrastructure but a somewhat diminished lectin binding activity, which was overcome by using long incubation times and high concentrations of reagents. Parietal cells reacted strongly with Bandieraea simplicifolia, Dolichos biflorus, peanut agglutinin, and soybean agglutinin (all specific for galactosyl/galactosaminyl groups) and weakly with Ulex europaeus (specific for fucose). At the light microscopic level a beaded, perinuclear staining pattern was observed which, ultrastructurally, corresponded to an intense staining of intracytoplasmic canaliculi. The membranes of the intracytoplasmic canaliculi were characterized by an abundance of galactosyl residues, a paucity of fucosyl groups, and a lack of mannosyl and glucosyl residues. The biochemical and physiological significance of these findings is discussed.