Brush border membrane vesicles were purified from rabbit renal cortex using a calcium-precipitation procedure, and the uptake of carboxylic acids was determined by a rapid-filtration method. L-Lactate, pyruvate (monocarboxylic acids), and succinate (dicarboxylic acid) demonstrate features of Na+ cotransport: enhanced initial rate (1 s) of uptake with an inward Na+ gradient compared with the Na+-free control and transient accumulation of substrate within the vesicles. Kinetic parameters derived for L-lactate and succinate show that each substrate is transported via a single pathway and that the two substrates exhibit marginal cross-inhibition. A range of monocarboxylic acids including pyruvate and ketone bodies appear to interact with the monocarboxylic acid carrier. The kinetic of Na+-dependent pyruvate uptake suggest at least two transport pathways - namely, that this monocarboxylic shares both the mono- and dicarboxylic acid carriers. We conclude that isolated rabbit renal microvillus membranes possess independent transport systems for mono- and polycarboxylic acids.
|Original language||English (US)|
|Journal||American Journal of Physiology - Renal Fluid and Electrolyte Physiology|
|State||Published - 1982|
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