Lactate Transport in Rat Aorta

Ouabain (10 mM) and gramicidin (5 micrograms/ml) do not inhibit lactate uptake by rat aortic rings. This supports the interpretation that a Na+ gradient is not involved in lactate transport. Dinitrophenol (25 microM) fails to inhibit lactate uptake, suggesting that oxidative metabolism is not required for lactate uptake. DIDS (4,4'-diisothiocyano-2,2'-stilbenedisulfonate), quercetin, and alpha-cyano-4-hydroxy-cinnamate-agents that have been reported to inhibit lactate transport in other cell types-were ineffective in inhibiting lactate transport in rat aortic rings. Inhibition of lactate uptake by glyceraldehyde is not stereospecific, does not involve inhibition of glucose phosphorylation, and does not appear to involve interaction with membrane sulfhydryls. PCMBS (p-chloromercuribenzenesulfonate) does not markedly inhibit the initial rate of lactate uptake, but diminishes the lactate space at later times. Pyruvate, phenylpyruvate, and thiolactate inhibit lactate uptake, but propionate and glycolate are poor inhibitors.