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

¹EA 2991 "Sport, Performance et Santé," Faculté des Sciences du Sport, Université de Montpellier, 34090 Montpellier; ²EA 701 "Physiologie des Interactions," Hôpital Arnaud de Villeneuve, 34295 Montpellier; and ³Service Central de Physiologie Clinique, Centre d'Exploration et de Réadaptation des Anomalies du Métabolisme Musculaire, Centre Hospitalier Universitaire Lapeyronie, 34295 Montpellier, France

Submitted 12 September 2003 ; accepted in final form 27 April 2004

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.

monocarboxylate transporter; endurance; lactate metabolism; hypoxemia; hemorheology

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