Secretion of endogenous lectin by chicken intestinal goblet cells.

Abstract

The 2 lactose-binding lectins found in adult chicken intestine, chicken-lactose-lectin-I (CLL-I) and chicken-lactose-lectin-II (CLL-II), were localized within the vesicles of the mucin-secreting goblet cells by indirect immunofluorescence and immunoperoxidase staining methods. Attention was concentrated on CLL-II which is 200 times more abundant than CLL-I in adult intestine. The localization of CLL-II in secretory vesicles, combined with its demonstration on the intestinal epithelial surface by immune staining methods and by specific elution with lactose, suggested that at least a portion of the CLL-II in the vesicles was secreted by the goblet cells and then became associated with the mucosal surface. In support of this, treatment of isolated intestinal strips with a cholinergic agent, bethanechol (10-7 M) produced a small but significant increase in the amount of CLL-II that could be eluted from their surface with lactose. Secretion of lectin may occur in conjunction with mucin because both are localized in the secretory vesicles and CLL-I and CLL-II apparently bind to purified chicken intestinal mucin, which is a potent inhibitor of their hemagglutination activities. The mucin is 6 orders of magnitude more potent than lactose as a hemagglutination inhibitor of CLL-I or CLL-II on a molar basis and 3 orders of magnitude more potent when expressed per mole of hexose. CLL-II and perhaps CLL-I, are probably secreted from the goblet cells along with mucin. They may function in the organization of mucin for secretion and/or in its association with the intestinal mucosal surface.