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Journal of Nutrition Vol. 111 No. 11 November 1981, pp. 1861-1868
Copyright © 1981 by American Society for Nutrition
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Radiometric-Microbiologic Assay of Vitamin B-6: Analysis of Plasma Samples1

Tomas R. Guilarte2 and Patricia A. Mcintyre

Division of Radiation Health Sciences, Department of Environmental Health Sciences, The Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205

A radiometric microbiologic assay for the analysis of vitamin B-6 in plasma was developed. The method is based on the measurement of 14CO2 generated from the metabolism of DL-1-14C-valine (L-1-14C-valine) by Kloeckera brevis. The assay is specific for the biologically active forms of the vitamin, that is, pyridoxine, pyridoxal and pyridoxamine, and their respective phosphorylated forms. The biologically inert vitamin B-6 metabolite (4-pyridoxic acid) did not generate a response at concentrations tested. The radiometric technique was shown to be sensitive to the 1 nanogram level. Reproducibility and recovery studies gave good results. Fifteen plasma samples were assayed using the radiometric and turbidimetric techniques. The correlation coefficient was r = 0.98. Turbid material or precipitated debris did not interfere with the radiometric microbiologic assay, thus allowing for simplification of assay procedure.

KEY WORDS: • vitamin B-6 • radiometric

1 Supported by USDA Science and Education Administration grant 78-59-2243-0-1-013-1 from the Competitive Research Grants Office. Also supported by a graduate student (Dr. Guilarte) stipend from Cooperative Research 12-14-1001-1222 between Department of Environmental Health Sciences, Division of Radiation Health Sciences, The Johns Hopkins University School of Hygiene and Public Health, Baltimore and USDA Nutrient Composition Laboratory, Nutrition Institute, Beltsville, MD.

2 To whom reprint requests should be sent.

Manuscript received 16 March 1981.




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