Mehansho H, Buss D D, Hamm M W, Henderson L M
Biochim Biophys Acta. 1980 Aug 1;631(1):112-23. doi: 10.1016/0304-4165(80)90059-8.
Evidence, obtained with in situ perfused rat liver, indicated that pyridoxine is taken up from the perfusate by a non-concentrative process, followed by metabolic trapping. These conclusions were reached on the basis of the fact that at low concentrations (0.125 microM), the 3H of [3H]pyridoxine accumulated against a concentration gradient, but high concentrations (333 microM) of pyridoxine or 4-deoxypyridoxine prevented this apparent concentrative uptake. Under no conditions did the tissue water:perfusate concentration ratio of [3H]pyridoxine exceed unity. The perfused liver rapidly converted the labeled pyridoxine to pyridoxine phosphate, pyridoxal phosphate and pyridoxamine phosphate and released a substantial amount of pyridoxal and some pyridoxal phosphate into the perfusate. Since muscle and erythrocytes failed to oxidize pyridoxine phosphate to pyridoxal phosphate, it is suggested that the liver plays a major role in oxidizing dietary pyridoxine and pyridoxamine as their phosphate esters to supply pyridoxal phosphate which then reaches to other organs chiefly as circulating pyridoxal.
