Management of Pyridoxine and Pyridoxal in the Isolated Kidney of the Rat

Abstract

The vascularly perfused kidney of the rat was used to study the transport, metabolism, filtration, secretion, reabsorption and excretion of pyridoxine (PN) and pyridoxal (PL), independent of other tissues including erythrocytes. [³H]-PN or [³H]-PL was administered via the perfusate at concentrations ranging from 8 nmole to 20.75 µmole per 95 ml perfusate. After 30 minutes of perfusion with 8 nmole of [³H]-PN, 17.2% of the total ³H was found in the kidney. As the concentration of PN in the perfusate was increased the percentage found in the kidney decreased. This inverse relationship resulted primarily from saturation of PL kinase in the kidney. At all levels of administration approximately one-half as much ³H was found in the kidney after [³H]-PL administration as when [³H]-PN was given at the same concentration. In the case of PN the primary metabolite found in the kidney was PNP whereas when PL was administered, significant amounts of PLP, PMP and pyridoxic acid were found. A differential response in the renal tubular handling of PN and PL is also reported. At all levels of administration of PL, the majority of the vitamer filtered was reabsorbed. The same was the case at the lowest dosage, however, at higher concentrations there was a net secretion of PN into the urine via a saturable process, this could account for the observed ratio of greater than 1 of kidney/perfusate concentration of PN.