Lectins bind differentially to rat olfactory and nasal respiratory cilia and microvilli: A rapid-freeze freeze-substitution lowicryl K11M embedding and deep-etch study

Abstract

Olfactory cilia have membranes that contain odorant receptors and an apparatus to transduce the odorous message into a code comprehensible to the rest of the cell and the brain. Membranes of these cilia have a variety of cellsurface proteins to do this. Ultrastructural freeze-fracture and freeze-etch studies have implied that this is really true. Biochemical and electrophysiological studies on olfactory epithelia with lectins have suggested that a major part of these proteins are glycoproteins. Therefore, binding of colloidal-gold conjugated lectins was studied in cilia and microvilli of rat olfactory with cilia and microvilli of nasal respiratory epithelial surfaces as comparison. This was done in sections of rapidly-frozen, freeze-substituted specimens embedded in Lowicryl K11M or, for wheat germ agglutinin ( WGA) alone, in deep-etched replicas. Olfactory dendritic endings and cilia labeled with WGA and, faintly, with soybean agglutinin (SBA); olfactory supporting-celi microvilli bound only Dolichos biflorus agglutinin (DBA). Microvilli of an infrequent cell bound peanut agglutinin (PNA), SBA, and WGA. Relative to olfactory cilia these microvilli labeled more strongly with the last two lectins. The cell resembles a presumptive sensory oneR. Cilia of nasal respiratory cells bound WGA and, somewhat more weakly, PNA; microvilli of respiratory cells bound all four lectins. In respiratory ciliated cells cilia and microvilli of the same cell type showed a quite different pattern of labeling.