New metabolites of vitamin B/sub 6/ in cat urine

Plasma from adult cats and from humans with adult onset hypophosphatasia has low alkaline phosphatase activity and high pyridoxal phosphate (PLP). Since the cats do not show the bone disease seen in humans, the authors initiated a study of vitamin B/sub 6/ metabolism in cats. /sup 14/C-pyridoxine HCL was donated by Hoffmann LaRoche (Nutley, NJ) and purified by HPLC. Following oral doses of /sup 14/C-pyridoxine HCL ranging from .97 to 486 ..mu..mol, urinary pyridoxic acid (PA) accounted for only 1 to 5% of the dose. Cation exchange HPLC of the urine revealed about 50% of the dose in a very fast eluting peak (X) and another 20 to 25% of the dose in a very slow eluting peak (Y). X elutes faster than PLP, is stable in base, but is hydrolyzed by acid to pyridoxal and pyridoxine. These properties are similar to those of 3-sulfate esters. Y is not altered by treatment with acid or base. In cation-exchange HPLC Y does not elute with the common B/sub 6/ vitamers but does elute with N-methyl-pyrdoxine. Y moves with N-methyl-pyridoxine in 3 TLC solvents. Both Y and N-methyl-pyridoxine fail to give an orange spot with diazotized p-nitroaniline. Further attempts to characterize Xmore » and Y are in progress. The low concentrations of PA in cat plasma and urine suggest a very limited capacity to oxidize vitamin B/sup 6/. This limitation apparently forces the use of alternate metabolic pathways.« less