Renal lactate uptake during exercise in humans

Abstract

The Cori cycle is critical for lactate metabolism during exercise as attenuated lactate elimination contributes to the arterial lactate accumulation. We evaluated renal lactate elimination by measuring the arterial‐renal venous (a‐v) lactate difference at rest, following infusion of sodium lactate (0.5 mM) and during moderate cycling that elicited a heart rate of 123 ± 9 b·min−1(mean ± SEM) combined with sodium lactate infusion in nine healthy men. At rest, the a‐v oxygen content and the a‐v lactate differences were 0.8 ± 0.2 mM and 0.02 ± 0.02 mM, respectively. Following infusion of sodium lactate the arterial lactate and the a‐v lactate difference were elevated to 6.5 ± 0.4 mM (P < 0.05) and 0.2 ± 0.3 mM (P < 0.05), respectively. During exercise with sodium lactate infusion arterial lactate reached 7.1 ± 1.1 mM (P < 0.05) and the a‐v oxygen content difference increased to 2.6 ± 0.8 mM (P < 0.05), indicating a 70% reduction of renal blood flow. The a‐v lactate difference increased to 0.5 ± 0.8 mM but was not significantly different from the pre‐exercise level and lactate uptake was not different during exercise than at rest with sodium lactate infusion suggesting that renal lactate uptake is driven by the lactate arterial concentration. In conclusion, during moderate exercise renal lactate extraction increases as renal blood flow is reduced by 70% and lactate uptake is maintained.