Transport and metabolism of pyridoxine in the intestine of the mouse.

The absorption of pyridoxine from the intestine of the mouse was studied in whole animals. [3H]Pyridoxine was orally administered and the distribution of isotope between the six recognized forms of vitamin B6 was determined in portal and peripheral blood after the administration. When small doses (1.4 or 14 nmol) were administered, labeled pyridoxine could hardly be found in the portal blood as well as in the peripheral blood, although labeled pyridoxal and pyridoxal phosphate were found both in the portal and peripheral blood. However, when a large amount (46 or 140 nmol) was given, a significant amount of labeled pyridoxine was found with labeled pyridoxal and pyridoxal phosphate both in the portal and peripheral blood. These results suggest that a physiological dose of pyridoxine is transformed to pyridoxal in the intestinal tissues and then is released in the form of pyridoxal into the portal blood.