Release of beta-D-galactoside-binding lectins into the cavities of aggregates of chick extraembryonic endoderm cells.

Dissociated cells from the extraembryonic endoderm of gastrulating chick embryos form aggregates when cultured in rotating flasks. The large cellular aggregates are initially solid but subsequently cavitate to form hollow, thin-walled vesicles. These cells also contain an endogenous beta-D-galactoside-binding lectin. Previous work has shown that high extracellular concentrations of this lectin are associated with decreased cell-cell adhesion [Milos, N. and S.E. Zalik: Differentiation 21, 175-182 (1982)]. We have removed the fluid contents from aggregates cultured for 24 and 48 h and tested them for the presence of lectin activity. The results demonstrate that lectin activity is detectable in a higher number of aggregates cultured for 24 as opposed to 48 h (75% vs. 28%, respectively). The lectin activity per aggregate is also higher in aggregates cultured for 24 h (180 vs. 67 hemagglutinating units, respectively, for 24- and 48-h aggregates). Thus, at the time when cells are moving apart from one another during aggregate cavitation, detectable lectin activity is released into the vesicular contents of the aggregate.