Effect of lactic acid on free fatty acids and glucose oxidation in dogs

Palmitate-1-C14 or glucose-C14(U) was infused intravenously for 4 hr at a constant rate in unanesthetized dogs with indwelling arterial and venous catheters. O2 uptake and CO2 output were measured. Specific activity of CO2 and of plasma FFA or plasma glucose was determined. Infusion of Na-l(+)-lactate greatly reduced the rate of release and uptake and the rate of oxidation of FFA in normal as well as in pancreatectomized dogs. Lactate decreased also the oxidation of plasma sugar but to a lesser degree. The elevated blood lactate seems to have a glucose-sparing effect in the resting dog. This may lead to accumulation of α-glycerophosphate and may explain the FFA-lowering effect of lactate. Na-d(–)-lactate infused in comparable concentration had no similar effect.