Opposite effects of in vitro lactate on erythrocyte deformability in athletes and untrained subjects.

Exercise transiently increases blood viscosity: however data on red cell deformability in this process remain inconsistent, since studies report either impairment (proportional to blood lactate accumulation), a lack of effect, or even in some cases an improvement. To test whether these inconsistencies may be due to physiological differences among populations studied, we compared the effects of in vitro lactate (2 mM, 4 mM and 10 mM) on erythrocyte rigidity in venous blood drawn at rest in 10 untrained vs 10 aerobically-trained subjects. After adjustment of osmolality and pH and incubation at 37 degrees C during 2 minutes, viscometric measurements were performed at 1000 s-1 with the MT90 (falling ball) viscometer and Dintenfass's 'Tk' was calculated.

Does exercise-induced hypoxemia modify lactate influx into erythrocytes and hemorheological parameters in athletes?

This study investigated 1) red blood cells (RBC) rigidity and 2) lactate influxes into RBCs in endurance-trained athletes with and without exercise-induced hypoxemia (EIH). Nine EIH and six non-EIH subjects performed a submaximal steady-state exercise on a cyclo-ergometer at 60% of maximal aerobic power for 10 min, followed by 15 min at 85% of maximal aerobic power. At rest and at the end of exercise, arterialized blood was sampled for analysis of arterialized pressure in oxygen, and venous blood was drawn for analysis of plasma lactate concentrations and hemorheological parameters.

Injections of recombinant human erythropoietin increases lactate influx into erythrocytes.

Previous studies showed that erythropoietin not only increases erythrocyte production but is also essential in both the synthesis and the good functioning of several erythrocyte membrane proteins, including band 3. It is still unknown whether anion and/or H(+) fluxes are modified by erythropoietin. This study aimed to evaluate the effect of recombinant human erythropoietin (rHuEPO) injections on lactate transport into erythrocytes via band 3 and H(+)-monocarboxylate transporter MCT-1, two proteins involved in lactate exchange.

Does haemorheology explain the paradox of hypoxemia during exercise in elite athletes or thoroughbred horses?

Exercise-induced arterial hypoxemia (EIAH), i.e., a significant drop of O2 arterial partial pressure during sea level exercise, has been shown in both aerobically trained athletes and athletic animal species.