Abstract

Reduced hepatic lactate elimination initiates blood lactate accumulation during incremental exercise. In this study, we wished to determine whether renal lactate elimination contributes to the initiation of blood lactate accumulation. The renal
arterial-to-venous (a-v) lactate difference was determined in nine men during sodium lactate infusion to enhance the evaluation (0.5 mol L71 at 16+1 mL min71; mean+s) both at rest and during cycling exercise (heart rate 139+5 beats min71). The renal release of erythropoietin was used to detect kidney tissue ischaemia. At rest, the a-v O2 (CaO2-CvO2) and lactate concentration differences were 0.8+0.2 and 0.02+0.02 mmol L71, respectively. During exercise, arterial lactate and CaO2-CvO2 increased to 7.1+1.1 and 2.6+0.8 mmol L71, respectively (P50.05),
indicating a *70% reduction of renal blood flow with no significant change in the renal venous erythropoietin concentration (0.8+1.4 U L71). The a-v lactate concentration difference increased to 0.5+0.8 mmol L71, indicating similar lactate
elimination as at rest. In conclusion, a *70% reduction in renal blood flow does not provoke critical renal ischaemia, and renal lactate elimination is maintained. Thus, kidney lactate elimination is unlikely to contribute to the initial blood lactate
accumulation during progressive exercise. Verf.-Referat