Pyridoxal-5-Phosphoric Acid in Whole Blood and Isolated Leukocytes of Man and Animals

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Abstract
Methods are described for the determination of pyridoxal-5-phosphoric acid (B6-PO4), codecarboxylase, in whole blood and in isolated leukocytes. While B6-PO4 is measurable in the blood of most animal species investigated, levels below the detection limit, i.e., less than 10 mµg/ml are found in over 80% of adult humans. Children up to about 18 months of age show readily measurable B6-PO4 levels in whole blood. Oral feeding of any form of vitamin B6 leads to a prompt rise in whole blood B6-PO4 in man, but a saturation level of about 60 mµg/ml is reached on feeding 4 to 7 mg of vitamin B6. The B6-PO4 content of leukocytes can be readily measured in the leukocytes isolated from 5 to 10 ml of human blood. In two large groups of adults an average of 0.15 ± 0.07 mµg of B6-PO4 per 106 leukocytes has been found. A significantly higher value was found in a group of New York school children (11 to 12 years) indicating the possibility of regression of leukocyte B6-PO4 with age. A sample of Cuban school children of the same age group showed even higher leukocyte B6-PO4 figures and the possible significance in terms of diet is discussed. A high percentage of very low leukocyte B6-PO4 values was found in a small group of arteriosclerotic patients. Additional data will be required to establish correlation between this finding and clinical observations.