Metabolism of 5'-deoxypyridoxine in rats: 5'-deoxypyridoxine 4'-sulfate as a major urinary metabolite.

5′-Deoxypyridoxine was taken up by rat liver and brain as rapidly as pyridoxine but was not retained by those tissues, an apparent consequence of its inability to form the 5′-phosphate derivative. More than 95% of the injected dose was excreted within 24 h. Practically no metabolism of 5′-deoxypyridoxine occurred in brain but in liver more than 95% was metabolized, mainly to two more electronegative compounds, one of which was identified as 5′-deoxypyridoxine 4′-sulfate. It accounted for more than 80% of the total urinary excretion of the antimetabolite. Almost no 5′-deoxypyridoxal was detected in liver, brain, or urine thus providing independent evidence for the concept that conversion of pyridoxine to pyridoxal-P occurs via pyridoxine-5′-P and that no mechanism exists in the rat for the direct oxidation of pyridoxine.