Abstract
Tritium-labeled pyridoxamine, pyridoxal 5′-phosphate, and pyridoxine 5′-phosphate were prepared and administered intravenously to mice, and the distribution of isotope in liver and carcass between pyridoxine, pyridoxine 5′-phosphate, pyridoxal, pyridoxal 5′-phosphate, pyridoxamine and pyridoxamine 5′-phosphate was determined at different times after administration. The vitamin B6 forms were extracted from the tissues by perchloric acid and separated by ion exchange chromatography. The results strongly suggest that phosphorylation is the first step in the conversion of pyridoxamine as well as of pyridoxine to the active coenzyme form of the vitamin. After an initial period of equilibration, pyridoxal 5′-phosphate and pyridoxamine 5′-phosphate accounted for more than 90% of recovered isotope in liver and for 80 to 90% of recovered isotope in carcass. The ratio between these compounds was about 2:1 in both liver and carcass. About 10% of the total isotope in carcass appeared as pyridoxal. The available experimental data obtained after administration of different forms of vitamin B6 were found to fit a kinetic metabolic model which assumes an equilibration between pyridoxal 5′-phosphate and pyridoxamine 5′-phosphate but essentially unidirectional reactions in other metabolic conversions.
Highlights
The vitamin B6 forms were extracted from the tissues by perchloric acid and separated by ion exchange chromatography
We have previously reported on the conversion of tritium-labeled pyridoxine into other forms of vitamin 116 in mouse liver and carcass [2]
P?Jridoxami?le-Pyridoxamine hydrochloride was labeled by exposure to tritium gas according to Wilzbach [4]
Summary
Tritium-labeled pyridoxamine, pyridoxal S/-phosphate, and pyridoxine 5’-phosphate were prepared and administered intravenously to mice, and the distribution of isotope in liver and carcass between pyridoxine, pyridoxine 5’-phosphate, pyridoxal, pyridoxal S/-phosphate, pyridoxamine, and pyridoxamine 5’-phosphate was determined at different times after administration. After an initial period of equilibration, pyridoxal 5’-phosphate and pyridoxamine S/-phosphate accounted for more than 90% of recovered isotope in liver and for 80 to 90% of recovered isotope in carcass. The ratio between these compounds was about 2: 1 in both liver and carcass. The available experimental data obtained after administration of different forms of vitamin B6 were found to fit a kinetic metabolic model which assumes an equilibration between pyridoxal 5’-phosphate and pyridoxamine 5’-. We have previously reported on the conversion of tritium-labeled pyridoxine into other forms of vitamin 116 in mouse liver and carcass [2]. On the basis of the reported results \ve have attempted to formulate a metabolic model for the interconversion of the different vitamin forms in liver
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