Reconstitution of the lactate carrier from rat skeletal-muscle sarcolemma

The lactate carrier was solubilized from purified rat skeletal-muscle sarcolemma with the detergent decanoyl-N-methyl-glucamide and the solubilized carrier was reconstituted into phospholipid vesicles. Reconstituted proteoliposomes showed a faster time course of L-lactate uptake than did protein-free liposomes. The rate of L-lactate uptake into the proteoliposomes was inhibited by the lactate-transport inhibitors p-chloromercuribenzenesulphonate, diethyl pyrocarbonate, alpha-cyano-4-hydroxycinnamate and quercetin. In contrast, the anion-exchange inhibitor DIDS (4,4'-di-isothiocyanostilbene-2,2'-disulphonate) had almost no effect on the uptake. The extent of L-lactate uptake at equilibrium was not affected by the presence of the transport inhibitors, but was sensitive to osmotic strength. L-Lactate and pyruvate, but not D-lactate, inhibited L-lactate uptake when present at 10-fold excess. The properties of L-lactate transport in reconstituted proteoliposomes were similar to those observed in native sarcolemmal vesicles, i.e. the lactate carrier seems to retain its transport characteristics during the solubilization and reconstitution steps.