Halothane does not inhibit synthesis of nucleic acids in Tetrahymena pyriformis

The effect of halothane on precursor incorporation into nucleic acids was studied in Tetrahymena pyriformis, a ciliate protozoan. At concentrations that blocked cell division (1.2 and 2.4 per cent), halothane inhibited incorporation of 14C-thymidine and 14C-uridine into DNA and RNA, respectively, in intact cells. However, in nuclei isolated from T. pyriformis, the anesthetic did not inhibit DNA and RNA synthesis when these processes were assayed using the nucleoside triphosphates (3H-thymidine triphosphate and 3H-uridine triphosphate) as precursors. It is concluded that halothane does not directly inhibit nucleic acid synthesis (i.e., the nucleic acid polymerase reactions), and that the inhibition of precursor incorporation observed in intact cells is due to an effect at a locus other than the DNA and RNA polymerase reactions.