By means of cryo-scanning electron microscopy (cryo-SEM) and fluorescent techniques, evidence is provided on how 12-O-tetradecanoylphorbol-13-acetate (TPA) affects Sertoli cell morphology and F-actin and vinculin organization in vitro. In order to visualize the morphological changes, the cells were observed with cryo-SEM. F-actin was localized using rhodamine (TRI)-phalloidin and vinculin using a primary monoclonal antibody and a second TRI-conjugated antibody. The results indicate that after the addition of 10(-7) M TPA, Sertoli cells begin to round up and their cytoplasm is retracted towards a central region. Actin bundle organization is disrupted and vinculin assumes a punctuate distribution throughout the cell. Thus, the reorganization of actin and vinculin and subsequent changes in cell morphology seem to be brought about by TPA affecting not only actin but also the protein vinculin which interacts with actin. A discussion is made concerning the effect of TPA on cytoskeletal reorganization, which is closely related to cell transformation.