Cell Killing and Mutation to 6-Thioguanine Resistance after Exposure to Tritiated Amino Acids and Tritiated Thymidine in Cultured Mammalian Cells (L5178Y)

Abstract
Cell killing and mutation to 6-thioguanine resistance were studied in growing mouse leukemia cells in culture after exposure to tritiated amino acids and tritiated thymidine. These effects varied widely among the tritiated compounds tested, being greatest for triated thymidine followed by tritiated arginine and tritiated lysine, in that order, for a given concentration of 3H expressed in kBq/ml of 3H in the medium. The differences between each tritiated amino acid disappeared almost totally when the effects were compared on the basis of the absorbed dose to the cells. The effects of tritiated thymidine, however, remained more than twofold greater compared to other tritiated compounds. These results indicate the importance of determining the absorbed dose for assessement of the radiotoxicity of tritiated organic compounds. For an exceptional case (tritiated thymidine), contribution of a mechanism(s) other than .beta. irradiation should also be taken into account.

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