The effects of topoinhibition and cytochalasin B on metabolic cooperation.

Metabolic cooperation was used to investigate the ability of 3T3 cells to form intercellular junctions under conditions of topoinhibition and topostimulation, respectively. A transformed BHK cell lacking hypoxanthine guanosine phosphoribosyl tranferase, which was used an an indicator, was found to incorporate 3H-hypoxanthine when in prolonged (20 hr) or brief (1 hr) contact with donor 3T3 cells, whether the latter were in a quiescent layer of in the region of stimulation at the edge of a wound. Cytochalasin B (1 mug/ml) prevented the development of metabolic cooperation and abolished most preexisting cooperation between donor 3T3 cells and recipient BHK cells. Cooperation was reestablished by removal of the drug. Cytochalasin B inhibited cooperation by the donor 3T3 cells in both the layer and wound edges, irrespective of topoinhibition and topostimulation. This provides further evidence that alteration in capacity to form stable intercellular junctions is not a necessary feature of the topoinhibition phenomenon.