D- and L-Lactate Catabolism to CO 2 in Rat Tissues 1 2

Abstract

The current study was initiated in order to compare the rates of oxidative catabolism of D- and L-lactate in various rat tissues. Uniformly labeled D- or L-[¹⁴C]lactate was incubated at 37°C in a closed system with tissue homogenates in Krebs-Ringer phosphate buffer. Evolved ¹⁴CO₂ was trapped in a center well containing a fluted filter paper saturated with strong base and the radioactivity determined. The ratio of L-lactate to D-lactate oxidation was greatest in brain, followed by kidney, heart, and liver. In liver the rate of oxidation of D-lactate exceeded that of L-lactate, in heart the rates were not significantly different and in the other two tissues L-lactate was oxidized more rapidly than D-lactate. These results indicate that the rate of D-lactate catabolism is considerable and is relatively greater than had been reported previously.