Comparing the impact of an acute exercise bout on plasma amino acid composition, intraerythrocytic Ca(2+) handling, and red cell function in athletes and untrained subjects.
The N-methyl d-aspartate receptors (NMDARs) mediating Ca(2+) uptake upon stimulation with glutamate and glycine were recently discovered in red blood cells (RBC) of healthy humans. Activation of these receptors with agonists triggered transient Ca(2+)-dependent decrease in hemoglobin oxygen affinity in RBC suspension. The aim of this study was to assess the potential physiological relevance of this phenomenon. Two groups formed by either healthy untrained volunteers or endurance athletes were subjected to a stepwise incremental cycling test to exhaustion. Plasma glutamate levels, activity of the NMDARs, and hemoglobin O2 affinity were measured in blood samples obtained before and after the exercise in both groups. Increase in plasma glutamate levels following exercise was observed in both groups. Transient Ca(2+) accumulation in response to the NMDAR stimulation with NMDA and glycine was followed by facilitated Ca(2+) extrusion from the RBC and compensatory decrease in cytosolic Ca(2+) levels. Short-term activation of the receptors triggered a transient decrease in O2 affinity of hemoglobin in both groups. These exercise-induced responses were more pronounced in athletes compared to the untrained subjects. Athletes were initially presented with lower basal intracellular Ca(2+) levels and hemoglobin oxygen affinity compared to non-trained controls. High basal plasma glutamate levels were associated with induction of hemolysis and formation of echinocytes upon stimulation with the receptor agonists. These findings suggest that glutamate release occurring during exhaustive exercise bouts may acutely facilitate O2 liberation from hemoglobin and improve oxygen delivery to the exercising muscle.
Institute of Veterinary Physiology and the Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland.
Asya
A
Makhro
Institute of Veterinary Physiology and the Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland.
Thomas
T
Haider
Institute for Molecular Cell Biology and Research Center for molecular Imaging and Screening, School of Medicine, Saarland University, Homburg, Germany.
Jue
J
Wang
Institute of Veterinary Physiology and the Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland.
Nikolay
N
Bogdanov
Experimental Physics, Saarland University, Saarbrücken, Germany.
Patrick
P
Steffen
Experimental Physics, Saarland University, Saarbrücken, Germany.
Christian
C
Wagner
Institute of Sports and Preventive Medicine, Saarland University, Saarbrücken, Germany.
Tim
T
Meyer
Institute of Veterinary Physiology and the Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland.
Max
M
Gassmann
Institute of Sports and Preventive Medicine, Saarland University, Saarbrücken, Germany.
Anne
A
Hecksteden
Institute for Molecular Cell Biology and Research Center for molecular Imaging and Screening, School of Medicine, Saarland University, Homburg, Germany; Experimental Physics, Saarland University, Saarbrücken, Germany.
Lars
L
Kaestner
Institute of Veterinary Physiology and the Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland. Electronic address: annab@access.uzh.ch.
Anna
A
Bogdanova
D000328:Adult; D000596:Amino Acids / Q000097:blood*; D056352:Athletes; D002118:Calcium / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D055815:Young Adult
D000596:Amino Acids; D002118:Calcium
Calcium; Exercise; NMDA receptors; Oxygen delivery; Red blood cells