Rapid uptake and clearance of pyridoxine by red blood cells in vivo.

ABSTRACT

There is rapid pyridoxine (PN) uptake in vitro into red cells where it is converted to pyridoxal (PL) forms. To assess uptake in vivo, the equivalent of 48.6 and 118 mumol PN were given intravenously to a healthy female subject. Vitamin B-6 compounds were measured by a Lactobacillus casei microbiological assay in blood taken 1-60 min after injection. After either injection there was a considerable amount of PN in the red cells at 1 min but by 3 min a large amount of that PN had disappeared, mostly unaccounted for by conversion to PL forms. Although there was considerably less PN at 1 min in both red cells and plasma after the smaller injection, in the next 2 min similar amounts had left the red cells (4.59 and 4.30 mumol) and plasma (9.37 and 10.09 mumol), respectively, after the injections. Red cells, as well as plasma, may be transporting PN to other sites of metabolism in tissues.