Metabolism of Lactate Isomers by Rumen Mucosa

Sheets of rumen epithelium from several ruminant species were incubated with L-lactate or D-lactate as the only added substrate offered over a wide concentration range. With increasing concentrations of L-lactate, increasing amounts of carbon dioxide were produced, usually more acetoacetate was synthesized, and more oxygen was taken up by the tissue. With increasing concentrations of D-lactate as a substrate, carbon dioxide production was increased, but formation of ketone bodies and oxygen uptake showed no direct relationship with the substrate level. The rate of carbon dioxide formation from D-lactate was generally lower than that from the L-isomer.