Metabolism of vitamin B 6 in the I-strain mouse : I. Absorption, excretion, and conversion of vitamin to enzyme co-factor

Abstract

The I-St strain mouse is an inbred strain whose elevated requirement for vitamin B 6 and whose acute sensitivity to audiogenic seizures is confirmed in experiments described here. We have compared vitamin B 6 metabolism in the I strain mouse to that in a control strain, the C57B1/6J, to determine whether abnormalities can be detected in absorption, excretion, or in the ability to convert vitamin B 6 to the major co-factor form, pyridoxal phosphate. We have also compared the two strains with regard to the activity of glutamic acid decarboxylase, a pyridoxal phosphate enzyme in brain which may regulate neuroirritability. No physiologically significant differences between the two strains were observed in absorption of the vitamin or in the ability to convert dietary vitamin B 6 to enzyme co-factor. Both the activity of glutamic acid decarboxylase and the degree of saturation of the enzyme with pyridoxal phosphate were similar in the two strains. When mice were fed a vitamin B 6-deficient ration high in protein, increased urinary losses of vitamin B 6 were observed in I strain mice as compared to C57 mice. This difference in excretion of vitamin B 6 is explored in detail in an accompanying paper.