Inhibition of smooth muscle cell proliferation and protein kinase C activity by tocopherols and tocotrienols.

alpha-Tocopherol, the most active form of vitamin E, causes a dose-dependent inhibition of serum-induced proliferation of smooth muscle cells (A7r5) in culture. Some tocopherol-related compounds exhibiting various degrees of antioxidant potency have also been tested on cellular proliferation. No direct correlation between the antioxidant activity of these compounds and their effect on smooth muscle cell growth could be observed. While most of the derivatives employed were not effective in inhibiting protein kinase C, in the case of alpha-tocopherol the antiproliferative effect was found to be parallel to the inhibition of protein kinase C activity, as measured in streptolysin-O permeabilized cells.