Vitamin B-6 Content of Plasma of Domestic Animals Determined by HPLC, Enzymatic and Radiometric Microbiological Methods

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Abstract
In the course of searching for a good animal model of human vitamin B-6 metabolism, it was discovered that plasma from pigs fed natural diets contained substances that interfered with the HPLC analysis of vitamin B-6. To determine the extent of such interference, plasma from several other species was examined. In addition to the HPLC method, the samples were analyzed by an apotyrosine decarboxylase method and a radiometric microbiological assay. In cats and dogs good correlation was obtained between pyridoxal phosphate concentrations determined by the HPLC and by the enzymatic method (r = 0.973). Also there was good correlation between total vitamin B-6 concentrations determined by HPLC and by radiometric microbiological assay (r = 0.998). Severe interference in the HPLC assay was encountered in plasma from pigs and herbivorous animals including goats, cattle, horses and sheep. The interference was eliminated in a pig fed a purified diet for 5 days. Average plasma pyridoxal phosphate concentrations range from 29 nM in pigs to 2443 nM in cats. This wide range indicates that there may be significant differences between species in dietary B-6 intake and/or metabolism of vitamin B-6.