Relationships between Vitamin B6-vitamer Content and the Activities of Two Transaminase Enzymes in Rat Tissues at Varying Intake Levels of Vitamin B6

Abstract

To study relationships between the vitamin B6-vitamer content of rat tissues to the activities of 2 transaminase enzymes in those tissues, and the relative biological activity of 3 vitamin B6-vitamers in the rat, we arranged to study, in depth 7 groups of rats that were fed diets containing (µg/g diet) 0, 0.5, 1.0, 2.0, and 10.0 of pyridoxol·HCl and 1.0 of pyridoxal·HCl or pyridoxamine·2HCl. Although a dietary level of 2.0 µg/g diet of pyridoxol was adequate to support maximal growth, higher tissue levels of total vitamin B6 and of the individual vitamers were reached at the 10.0 µg/g diet level, in liver, kidney, brain, muscle, and heart. Of the 3 vitamin B6 vitamers, pyridoxamine was depleted to the greatest extent, as percentage, at lower levels of dietary pyridoxol. In studies on glutamic-pyruvic (GPT) and glutamic-oxalacetic transaminase (GOT) activities in the above tissues plus plasma and red blood cells, enzyme activity increased with increased dietary pyridoxol and with increased tissue vitamin B6 content. GPT was depleted to a greater extent than, and GOT to a lesser extent than, the percentage depletion for tissue vitamin B6 at lower levels of pyridoxol intake. It appeared from studies on growth, tissue content of vitamin B6 and vitamers, and tissue transaminase activity, that at the level of 1.0 µg/g diet, pyridoxal was essentially equivalent to pyridoxol for vitamin B6 activity; the study on pyridoxamine required re-evaluation. A simplified medium was used for the microbiological portion of the assay of the vitamin B6 vitamers.