Tocopherol Modulates the Effects of A23187, Verapamil, and Phorbol Myristate Acetate on RNA-Polymerase Activity of Isolated Rat Liver Nuclei

A. A. Kapralov,^1,2 G. V. Petrova,³ S. M. Vasilieva,³ and G. V. Donchenko³

¹Institute of Physiology, Shevchenko Kiev University, ul. Vladimirskaya 64, Kiev, 252033 Ukraine; fax: (044) 266-21-29.

²To whom correspondence should be addressed.

³Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, ul. Leontovicha 9, Kiev, 252030 Ukraine; fax: (044) 229-63-65.

Submitted July 26, 1996; revision submitted December 9, 1996.

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Preincubation of rat liver nuclei with tocopherol decreased inhibition of RNA-polymerase activity of isolated rat liver nuclei by A23187, verapamil, and phorbol myristate acetate (PMA). In nuclei of vitamin E-deficient rats, A23187, verapamil, and PMA did not inhibit label incorporation into RNA with and without tocopherol. A23187, verapamil, and PMA did not inhibit the activity of nuclei treated with 1% Triton X-100; tocopherol activated RNA synthesis but co-administration of A23187 or verapamil and tocopherol had no effect and the combination of tocopherol and PMA inhibited RNA-polymerase activity by 25%. The effect of the combination of verapamil and PMA in the presence of free tocopherol was different from the effect of these compounds assayed in the presence of the complex of tocopherol with tocopherol-binding protein.

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KEY WORDS: alpha-tocopherol, tocopherol-binding proteins, RNA-polymerase activity, nuclei, A23187, verapamil, phorbol myristate acetate.

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