Induction of cell division in olfactory basal epithelium following intranasal irrigation with wheat germ agglutinin-horseradish peroxidase

The lectin, wheatgerm agglutinin (WGA) conjugated to horseradish peroxidase (HRP), previously was shown to be transported into the central nervous system following application by intranasal irrigation. The current study investigated the hypothesis that uptake of molecules, such as the lectin-conjugate, by olfactory receptor cells would mimic internalization of other substances including odorants. This process would result in both premature death of receptor cells and increased turnover of their precursors, globose basal cells. Tetramethylbenzidine histochemical analysis showed the presence of significant amounts of the lectin-conjugate in both the receptor epithelium and olfactory bulb until at least 2 weeks postintranasal application. Neither supporting nor globose basal cells contained WGA-HRP, suggesting that uptake was primarily into olfactory receptor cells. Cell turnover, assessed by tritiated-thymidine (thymidine) autoradiography, increased both 1 and 2 weeks, but not 3 and 4 weeks, following intranasal irrigation with WGA-HRP. Most of the cells containing thymidine labelling appeared to be globose basal cells, although supporting cells also occasionally exhibited labelling. Survival of either mature or immature receptor cells in the epithelium, indicated by epithelial thickness and cell density of the septal epithelium, also declined following treatment. These data suggest that uptake of substances may result in cell loss from the olfactory epithelium and increased mitotic activity of basal cells. (C) 1998 Wiley-Liss, Inc.