Effect of lactate infusion on myocardial FFA metabolism in diabetic dogs

The effect of elevated arterial lactate concentration on myocardial free fatty acid (FAA), acetoacetate (AcAc), and beta-hydroxybutyrate (beta-OHB) uptake was studied in alloxan-diabetic dogs under control conditions and following the constant infusion of Na-L-(+)-lactate. Only minor changes in hemodynamic parameters were observed. During lactate infusion, arterial lactate increased and FFA, AcAc, and beta-OHB decreased. The extraction ratio and myocardial uptake of both AcAc and beta-OHB diminished. No significant change of myocardial FFA oxidation was noted. While myocardial lactate uptake was very small under control conditions, it increased considerably during the infusion of lactate. The fraction of myocardial CO2 production derived from FFA oxidation was unchanged during lactate infusion, while the fraction derived from ketone bodies decreased and that derived from lactate increased. Thus, during hyperlactacidemia a larger fraction of myocardial substrate was derived from lactate and a smaller fraction from ketone bodies than were derived under control conditions.