A quantitative freeze-etching study on the effects of cytochalasin B, colchicine and concanavalin A on the formation of intercellular contacts in vitro.

The effects of concanavalin A (conA), cytochalasin B (CB), and colchicine acting on cell membrane-associated structures, such as surface receptors or submembranal cytoskeletal components, were studied in trypsin-isolated plexus cells reaggregated in vitro. Following reaggregation, these cells form intercellular contacts, i.e. a zonula occludens (ZO) and integrated nexus (gap junctions, GJ). In the control cultures the GJ occupied 4.7%, the tight junctions (TJ) occupied 14 microns/microns2 of the surface of the zonula occludens (ZO). All the drugs/lectins studied inhibit contact formation in a characteristic manner. ConA inhibits the formation of GJ (1% of the ZO) and causes 5 times more defective TJ strands than the controls. CB inhibits the assembly of the TJ (75% of the controls) and the GJ (1% of the ZO) when it is administered during the period of contract formation. Colchicine inhibits the formation of GJ (1% of the ZO) and produces 2.5 times more open-end strands of TJ than the controls. All effects are reversible with the exception that integrated GJ are not re-formed after colchicine administration. It is suggested that an intact interaction between surface receptors, intramembranous particles and associated cytoskeletal structures is necessary for remodelling cellular contacts.