The fate of dietary pyridoxine-beta-glucoside in the lactating rat.

[3H]5'-O-(beta-D-glucopyranosyl) pyridoxine (PN-glucoside) and [14C]pyridoxine (PN) were orally administered to lactating rats. Milk was collected from the dam, and the stomach contents and liver were collected from the suckling pups 24 and 48 h after administration. Analysis of the isotopic ratio (3H/14C) in the milk and stomach contents indicated that the secretion of 3H in the milk was 20-25% as great as the secretion of 14C. The only labeled form of 3H and 14C in the stomach contents was pyridoxal phosphate (PLP), indicating that PN-glucoside was hydrolyzed to PN and subsequently metabolized prior to secretion by the mammary gland. The isotopic ratio in the livers of the pups was similar to that of the stomach contents. Furthermore, the relative distribution of the two isotopes among the hepatic metabolites of the pups was similar. The results of this study indicate that intact PN-glucoside is not secreted in milk, although vitamin B-6 derived from the limited hydrolysis and metabolism of PN-glucoside is delivered to the mammary gland for secretion.