The Distribution of Vitamin B, in the Tissues of Two Inbred Strains of Mice Fed Complete and Vitamin Bddeficient Rations *

The classical studies of Rabinowitz and Snell (1) demonstrated that vitamin Be exists in at least three forms in the tissues of animals and plants: pyridoxine, pyridoxamine, and pyridoxal. Their assay procedure, a differential growth response of microorganisms to pyridoxine, pyridoxamine, and pyridoxal, would not differentiate between the phosphorylated and the nonphosphorylated forms of the vitamin. Recently, a method for the complete separation of all six forms of the vitamin has been developed here, and it was found that pyridoxamine 5’-phosphate and pyridoxal 5’-phosphate are the predominant forms of the vitamin present in mammalian cells (2). Variations in the distribution of pyridoxamine 5’-phosphate and pyridoxal 5’-phosphate were evident in preliminary studies (2) on two highly inbred strains of mice, the C57 and the I, which also exhibit marked differences in the metabolism of vitamin Bg (3). A thorough study on the distribution of pyridoxamine 5’-phosphate and pyridoxal 5’-phosphate in these animals was therefore warranted. Further, since the I strain mouse gains less weight when fed high protein diets (4) and has a higher turnover of protein (5) than the C57 strain mouse, we speculated on the possibility that the relative amounts of pyridoxamine 5’.phosphate and pyridosal 5’-phosphate could act as a controlling factor in metabolism. The data presented here demonstrate that in the liver the levels of pyridoxal 5’-phosphate and pyridoxamine 5’-phosphate are different in the two strains of mice when they are fed complete rations, although the total amounts of vitamin Bg are similar. Further, the proportionate loss of pyridoxal 5’-phosphate is greater in the brain of vitamin Be-deficient mice of the I strain. This observation may be a partial explanation for the early susceptibility of the deficient I strain mouse to audiogenic seizures.