Transport of l-arginine in brush border vesicles derived from rabbit kidney cortex

Abstract

The uptake of l-arginine by brush border vesicles from rabbit kidney cortex was investigated at 37 °C and pH 7.5. The initial rate of uptake (15 s) was twice as fast in a highly purified brush border as in brush border contaminated by basal-lateral plasma membranes. The initial uptake in a mannitol medium can be best described as the sum of transfer by two systems with K m values of 0.07 and 3.5 m m and V max values of 1.5 and 8 nmol/mg protein × 15 s, respectively. For the inhibitors of l-[ 14C]arginine, uptake (15 s at two substrate concentrations of 0.1 and 2.5 m m in a mannitol medium) the following sequence of inhibitory strength was established: l-arginine, l-ornithine, l-cystine, l-lysine, d-arginine, and NaCl. When a vesicular membrane potential was induced transiently by a jump of the pH in the incubation medium from 5.9 to 7.5 or by an outward movement of K + in the presence of gramicidin D, an overshoot of l-arginine uptake was observed. Initial uptake of l-arginine was slightly faster in the presence of a Na + gradient (outside to inside) than under a K + gradient. Both ion gradients reduced uptake as compared to the uptake in a mannitol medium. Uptake was also studied after the membrane potential was minimized by equilibrating the vesicles in a NaCl or KC1 medium in the presence of gramicidin D. Under these conditions, l-arginine uptake in the first 30 s was faster in the NaCl than in the KCl medium. These experiments indicate, beside a major ion-independent l-arginine transport, the presence of a transport stimulated by Na + in isolated brush border vesicles.