The effects of increased osmotic pressure on focal contacts and microfilament bundles of cultured fibroblasts

Incubation of normal substrate-spread mouse fibroblasts in hypertonic medium containing 0.25 M sorbitol leads first to partial shrinkage of cytoplasm, but later the cells restore the normal flattened cell shape. However, these sorbitol-incubated cells, in contrast to control cells, had no discrete bundles of microfilaments and considerably a diminished number of focal cell-substrate contacts. Thus, by incubation with sorbitol, distribution of actin microfilaments and morphology of cell-substrate contacts can be switched from one pattern to another without concomitant changes of the cell shapes.