Mediated transport and metabolism of lactate in rat aorta.

1. Under appropriate conditions L- and D-lactate enter the cells of rat aorta and are metabolized. Oxidation of lactate to CO2 occurs under aerobic conditions. 2. L- and D-lactate are taken up into the cells when oxygen, glucose, or both oxygen and glucose are present in the incubation medium. Both L- and D-lactate are excluded from the cells when neither oxygen nor glucose is present. 3. D,L-Glyceraldehyde prevents the uptake of L-lactate. The effect is apparently not due to the inhibition of glucose metabolism by L-glyceraldehyde. 4. L-lactate (20 mM) markedly inhibits the uptake of 5 mM D-lactate, but 20 mM D-lactate fails to inhibit the uptake of 5 mM L-lactate. 5. Raising the pH of the incubation medium markedly depresses the uptake of L-lactate. 6. The results provide evidence that L- and D-lactate enter the cells of rat aorta by a mediated transport system.