Response of B-6 vitamers in plasma, erythrocytes and tissues to vitamin B-6 depletion and repletion in the rat.

We determined the response patterns of B-6 vitamers in blood and tissues to vitamin B-6 depletion and repletion. B-6 vitamers were measured in plasma, erythrocytes, liver, muscle, kidney, heart, brain, spleen and lung by reverse-phase high performance liquid chromatography in male rats pair-fed control or vitamin B-6-deficient diets for 2 or 4 wk, or for 4 wk followed by 1 wk of repletion with the control diet (n = 4/group). Food intake (15.6 +/- 0.3 g/d, mean +/- SEM; n = 28) and body weight (190 +/- 2 and 290 +/- 5 g at wk 0 and 5, respectively; n = 28) of control groups were not different from those of deficient groups throughout the study. After 2 wk of vitamin B-6 depletion, tissue concentrations of pyridoxal phosphate (PLP) and pyridoxamine phosphate (PMP) were about 50% and 10-40% lower, respectively, in the deficient than in the control group (except for spleen PMP); in plasma and erythrocytes, PLP and pyridoxal concentrations were about 90% lower in the deficient group. Differences in vitamer concentrations between control and deficient groups were not larger after 4 wk of depletion than after 2 wk. Vitamer concentrations in plasma, erythrocytes and all tissues returned to control levels after 1 wk of repletion with the control diet. These results demonstrate that B-6 vitamers in blood and tissues of the rat respond quickly and reversibly to changes in dietary vitamin B-6, with larger percentage changes occurring in plasma and erythrocytes than in tissues.