Effects of 12-0-tetradecanoyl-phorbol-13-acetate on oral epithelium in vitro.

TPA, a tumor promotor whose initial site of action is the cell membrane, was examined for its actions on hamster oral mucosa using light and scanning electron-microscopic procedures. Hamster cheek-pouch explants were cultured in vitro, then treated for 72 h with 1.6 X 10(-8) M TPA. Treated cultures showed a higher mitotic index and more extensive growth than control cultures. Epithelial cells in the control cultures appeared polygonal, with thin, small to medium microvilli. The cells in the treated cultures showed variable shape and surface morphology. Some were interconnected by broad cytoplasmic extensions while others demonstrated long, thin processes that traversed great distances. The unusual surface morphology may be a manifestation of altered phospholipid metabolism that produces a more "fluid" cytoplasmic membrane.