title: Does exercise-induced hypoxemia modify lactate influx into erythrocytes and hemorheological parameters in athletes?
abstract: 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. Lactate influxes into RBCs were measured at three labeled [U-14C]lactate concentrations (1.6, 8.1, and 41 mM) on venous blood sampled at rest. The EIH subjects had higher maximal oxygen uptake than non-EIH (P < 0.05). Total lactate influx was significantly higher in RBCs from EIH compared with non-EIH subjects at 8.1 mM (1,498.1 +/- 87.8 vs. 1,035.9 +/- 114.8 nmol.ml(-1).min(-1); P < 0.05) and 41 mM (2,562.0 +/- 145.0 vs. 1,618.1 +/- 149.4 nmol.ml(-1).min(-1); P < 0.01). Monocarboxylate transporter-1-mediated lactate influx was also higher in EIH at 8.1 mM (P < 0.05) and 41 mM (P < 0.01). The drop in arterial oxygen partial pressure was negatively correlated with total lactate influx measured at 8.1 mM (r = -0.82, P < 0.05) and 41 mM (r = -0.84, P < 0.05) in the two groups together. Plasma lactate concentrations and hemorheological data were similar in the two groups at rest and at the end of exercise. The results showed higher monocarboxylate transporter-1-mediated lactate influx in the EIH subjects and suggested that EIH could modify lactate influx into erythrocyte. However, higher lactate influx in EIH subjects was not accompanied by an increase in RBC rigidity.
authors.affiliation: EA 2991 Sport, Performance et Santé, Faculté des Sciences du Sport, Université de Montpellier, 34295 Montpellier, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Connes
authors.forename: Didier
authors.initials: D
authors.lastname: Bouix
authors.forename: Guillaume
authors.initials: G
authors.lastname: Py
authors.forename: Corinne
authors.initials: C
authors.lastname: Caillaud
authors.forename: Pascale
authors.initials: P
authors.lastname: Kippelen
authors.forename: Jean-Frédéric
authors.initials: JF
authors.lastname: Brun
authors.forename: Alain
authors.initials: A
authors.lastname: Varray
authors.forename: Christian
authors.initials: C
authors.lastname: Prefaut
authors.forename: Jacques
authors.initials: J
authors.lastname: Mercier
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001809:Blood Viscosity; D004912:Erythrocytes / Q000378:metabolism*; D005080:Exercise Test; D006400:Hematocrit; D018056:Hemorheology / Q000379:methods; D006801:Humans; D000860:Hypoxia / Q000097:blood* / Q000209:etiology / Q000503:physiopathology*; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D027501:Monocarboxylic Acid Transporters / Q000737:chemistry*; D010101:Oxygen Consumption; D010807:Physical Endurance; D005082:Physical Exertion; D013177:Sports; D027981:Symporters / Q000737:chemistry*; D000099233:Monocarboxylate Transport Protein 1
chemical_list: D019344:Lactic Acid; D027501:Monocarboxylic Acid Transporters; D027981:Symporters; D000099233:Monocarboxylate Transport Protein 1