H+-L-proline cotransport by vesicles from pars convoluta of rabbit proximal tubule.

The mechanism of renal transport of L-proline by luminal-membrane vesicles isolated from proximal convoluted tubules of rabbit kidney was studied. It was found that H+ gradient (extravesicular greater than intravesicular) can drive the transport of L-proline into the vesicles both in the presence and absence of Na+. The stimulation of L-proline uptake by a pH gradient was additive with that produced by Na+. Saturation kinetic experiments revealed that pH gradient, in addition to Na+, increased the maximal uptake of L-proline by twofold. This is the first demonstration of H+-L-proline cotransport across luminal membrane of rabbit kidney proximal convoluted tubule. The physiological importance of this system is briefly discussed.