Glutathione may inhibit sodium-dependent phosphate transport by renal brush-border membrane vesicles

Glutathione, a biological reductant, can affect certain aspects of transport function in renal cortical slices. The influence of glutathione on the rate of sodium-dependent phosphate uptake into renal brush-border membrane (BBM) vesicles was examined. Vesicles were obtained from rat renal cortex by the conventional calcium precipitation method. The amounts of GSH and oxi-glutathione were measured by chromatography. The vesicles were incubated for 15 min with glutathione (10 mM) prior to a 1-min influx of phosphate. The incubation with glutathione reduced the phosphate uptake from 1887 +/- 217 to 1496 +/- 116 pmol/mg (n = 5, p less than 0.05). A kinetic study revealed that the incubation with glutathione resulted in an increase of Km in the sodium-dependent phosphate transporter from 85 +/- 7.9 to 159 +/- 18 microM (n = 5, p less than 0.05). Glutathione was catabolized rapidly by the incubation with BBM, and a concomitant production of oxi-glutathione was recognized. Incubation with oxi-glutathione (10 mM) for 15 min, however, did not affect the phosphate uptake, the present results suggest that incubation with reduced-form glutathione decreases the affinity of the sodium-dependent phosphate transport across the renal brush-border membrane, and that catabolism of glutathione may be linked the inhibitory mechanism.