Early changes in plasma membrane in vitro by treatment with chemical carcinogen.

Abstract

: To examine early changes in the cell membrane caused by treatment with 9.10-dimethyl-1.2-benzanthracene (DMBA), rat lingual epithelium in vitro was observed by means of electrophysiological, freeze-fracture and whole mount electron microscopic methods. Membrane potential showed a transient decrease at 6 h after the treatment but returned to almost the same level as that of the control group 1 day later. Membrane resistance decreased rapidly at 6 h after the treatment but increased at 12 h. Transient decrease of membrane resistance and membrane potential occurred prior to the decrease in coupling ratio at 6 h after treatment with DMBA. In freeze-fracture replicas, after 6 h of treatment with DMBA, the number of intramembranous particles (IMPs) was less than that of the control. This decrease was especially pronounced on the P-face. After 12 h treatment with DMBA, the number of IMPs increased by 20-40 % more than the control value. This increase was especially noticeable on the E-face, which was 70 % of the control value. At 3 days and thereafter, the number of IMPs decreased again and remained approximately the same as that of the control, though the Eface values remained larger than those of the control.Treatment with DMBA had a marked effect on the cytoskeletal organization.Treatment with DMBA caused morphologic changes as early as 6 h. These early changes might represent triggers for subsequent metabolic cellular abnormalities. The affected cells which were treated with DMBA appear to differ from normal cells through accelerated-abnormal cell membrane and cytoskeletal turnover.