Pyridoxine-5'-beta-D-glucoside influences the short-term metabolic utilization of pyridoxine in rats

This study was conducted to characterize the initial time course of the apparent competitive effect of pyridoxine-5'-beta-D-glucoside against co-ingested pyridoxine. Two groups of rats were administered a single oral dose of 100 nmol of [14C]pyridoxine along with either 0 or 20 nmol of unlabeled pyridoxine-5'-beta-D-glucoside. At 6, 12, 24 and 48 h post-dose, the distribution of labeled vitamin B-6 metabolites in blood, tissues and urine was determined. Urinary [14C]4-pyridoxic acid comprised a significantly greater percentage of excreted 14C in the control group, with the greatest difference at 12 h post-dose. Pyridoxine-5'-beta-D-glucoside (10-15 nmol) was excreted mainly in unchanged form within 6 h. Rats that received pyridoxine-5'-beta-D-glucoside retained less 14C in liver, with a maximal difference between groups at 6-12 h post-dose. The relative concentrations of hepatic [14C]pyridoxal 5'-phosphate and [14C]pyridoxamine 5'-phosphate in the treatment group were greater than in the control group at approximately 12 h post-dose. At 48 h post-dose, there was no difference in the distribution of any vitamin B-6 metabolite except pyridoxal 5'-phosphate in the two groups. These results confirm that a small, nutritionally relevant dose of pyridoxine-5'-beta-D-glucoside influences the utilization of pyridoxine and indicate that this is a short-term, transient effect