Effect of vitamin B6 deficiency on in vitro uptake and metabolism of pyridoxine x HCL by rat jejunum.

The effect of vitamin B6 deficiency on the uptake and metabolism of pyridoxine x HCl by rat jejunum was studied in vitro utilizing everted sacs. Rats were studied in three grops: control, B6-replenished, and B6-deficient. Plasma and jejunal tissue pyridoxal phosphate levels in deficient rats were profoundly depressed compared to control and replenished groups. Uptake and phosphorylation rates for pyridoxine x HCl were similar among the three groups. Jejunal pyridoxal phosphate levels were unchanged after incubation of sacs from control and replenished rats for 30 min in 2 and 20 micro M pyridoxine x HCl under low phosphate (1.1 mM) conditions. Jejunal pyridoxal phosphate significantly increased, however, during similar 30-min incubations in sacs of deficient rats under low phosphate conditions and in control sacs under high phosphate (80 mM) conditions. Conclusions are 1) in vitro uptake and phosphorylatin remain intact during vitamin B6 deficiency; 2) jejunal pyridoxal phosphate is maintained at a constant level in sacs from control and replenished rats in spite of ongoing uptake and phosphorylation of pyridoxine; 3) jejunal pyridoxal phosphate significantly increases during incubationin sacs from vitamin B6-deficient rats; and 4) absorbed pyridoxine can serve directly as the source for this increase.