Enflurane Effects on Cell Division and Macromolecular Synthesis in Tetrahymena pyriformis

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Abstract
The objectives of this study were to determine the effects of enflurane on cell division and incorporation of macromolecular precursors into nucleic acid of T. pyriformis, to determine the effects of both enflurane and halothane on incorporation of amino acids into proteins of T. pyriformis and to compare the effects of these 2 anesthetics using these data and data previously reported for halothane. After exposure for 3 h, cell division was inhibited 66 and 81% by enflurane, 2.2 and 4.3%, respectively. Exposure for 3 h resulted in 25 and 81% inhibition of 14C-thymidine incorporation and 74 and 98% inhibition of 14C-uridine incorporation by enflurane, 2.2 and 4.3%, respectively. Enflurane, as previously shown for halothane, did not inhibit DNA or RNA synthesis in isolated nuclei (assayed using 3H-labeled nucleoside triphosphates as precursors). Incorporation of 14C-amino acids was inhibited 17 and 60% by exposure for 3 h to halothane (1.2 and 2.4%, respectively) and 49 and 77% by exposure for 3 h to enflurane (2.2 and 4.3%, respectively). The comparison of halothane and enflurane was made to determine whether the effects on T. pyriformis were proportional to the absolute (percent or molar) anesthetic concentration, or to MAC (minimum alveolar concentration). Inhibition of cell division is proportional to MAC (i.e., equivalent inhibition is observed when the anesthetic concentration in the culture medium is the same as that in blood exposed to either 1 MAC halothane or 1 MAC enflurane), and that inhibition of macromolecular precursor incorporation (in intact cells) is proportional to the absolute (percent or molar) anesthetic concentration. Inhibition of cell division by the anesthetics is not due to direct inhibition of nucleic acid synthesis, nor is it directly related to inhibition of thymidine, uridine or amino acid incorporation in intact cells.

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