Metabolism of labeled pyridoxine in the rat

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Abstract
The excretion of labeled compounds in the urine was studied after administration of tritium -labeled pyridoxine to rats. The percentage of isotope excreted during the 1st day after the administration of the isotope was primarily dependent on total intake of pyridoxine and increased when increasing amounts of py -ridoxine were administered. The isotope excretion in the urine was followed for up to 20 days and found to occur with a half-life of 40-228 days after the 2nd day of the experiment. A simple model for the over -all metabolism of pyridoxine was used to calculate the fractional turnover rate of vitamin B6 (1.2-1.5%/day in the non-deficient animals) and to calculate the fractional rate of eminination of vitamin Bg from a postulated body reservior of the vitamin. The elimination rate (about 1%/day) was not significantly influenced by pyridoxine intake. 4-Pyridoxic acid has been determined in the urine and found to account for 10-30% of the daily elimination of the vitamin. On the basis of the metabolic model an attempt was made to calculate the amount of vitamin Bg derivatives in the body and elimination in the urine, which was 25-80 [mu]g/day in the nondeficient rats and 3-6 [mu]g/day in the Bg-deficient animals.