Trifluoperazine inhibits formation of adhesion plaque complexes and cell sorting in aggregates of fibroblasts.

Trifluoperazine (TFP) at 5 microM completely blocks the formation of adhesion plaque complexes (adhaerens junctions) between aggregating fibroblasts; the drug at this same concentration did not prevent the cells from producing aggregates of normal size and appearance. Implicit in this finding is that aggregation does not rely on adhesion plaque complex formation. When thymidine-3H labelled 16C and unlabelled BHK fibroblast cells were experimentally combined to form aggregates in which the cells were initially uniformly distributed, the 16C cells, which produced adhesion plaque complexes within minutes and in greater numbers than did BHK cells, congregated in an internal position after the aggregates had been cultured for 12h. This redistribution of the cells, indicated by the positioning of the labelled 16C nuclei, did not occur when the aggregates were exposed to TFP. Thus cell sorting, unlike aggregation, seems to be reliant on the formation of adhesion plaque complexes.