Sensitivity and Specificity of the Asplanchna Response to Dietary α-Tocopherol

Abstract

Dietary α-tocopherol induces the rotifer A. sieboldi to produce offspring with characteristic outgrowths of the body wall. A quantitative assay for vitamin E compounds, based on this response, is described and discussed. A minimal response in this assay was elicited with a dose of 5 × 10^-13 moles or 0.2 ng of d-α-tocopherol per female. The response increased in a roughly linear fashion until it became maximum at 5 × 10^-11 moles or 20 ng per female. The sensitivity of this biological assay for α-tocopherol is unique and is compared with that of other assay systems. Antioxidants (Ethoxyquin and Menadione), selenium (with and without methionine), hexahydro coenzyme Q₄, tocopheronolactone, N-methyl-γ-tocopheramine, 5,5′-methylene bis-(γ-tocopherol), and 2,5,7,8-tetramethyl-2-(4′,8′-dimethylnonyl)-6-hydroxychromane were completely inactive in the rotifer assay. α-Tocopherol levorotatory at the C-2 center had only 0.005% the activity of the d-epimer. Both dl-α-tocopheramine and α-tocopheryl quinone had 0.2% and the spiro dimer and 5,5′-Bi-α-tocopherol, respectively, had 0.1 and 0.02% of the activity of d-α-tocopherol. The specificity of the tocopherol molecule in the Asplanchna response appears to be as great as or greater than that in other known vitamin E-regulated responses. Finally, the advantages of the Asplanchna response as a biological assay for vitamin E compounds are discussed.