ORIGINAL ARTICLE Erythrocyte membrane fluidity and indices of plasmatic oxidative damage after acute physical exercise in humans C. Berzosa • E. M. Go´mez–Trulle´n • E. Piedrafita • I. Cebria´n • E. Martı ´nez–Balları ´n • F. J. Miana–Mena • L. Fuentes–Broto • J. J. Garcı ´a Accepted: 10 November 2010 / Published online: 30 November 2010 Ó Springer-Verlag 2010 Abstract Optimal levels of membrane fluidity are essential for numerous cell functions including cell growth, solute transport and signal transduction. Since exercise enhances free radical production, our aim was to evaluate in healthy male subjects the effects of an acute bout of maximal and submaximal exercise on the erythrocyte membrane fluidity and its possible relation to the oxidative damage overproduction due to exercise. Subjects (n = 34) performed three cycloergometric tests: a continuous pro- gressive exercise, a strenuous exercise until exhaustion and an acute bout of exercise at an intensity corresponding to 70% of maximal work capacity for 30 min. Venous blood samples were collected before and immediately after these exercises. Erythrocyte membrane fluidity was assessed by fluorescence spectroscopy. Plasma malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA) concentrations and carbonyl content of plasmatic proteins were used as an index of lipid and protein oxidation, respectively. Exercise produced a dramatic drop in the erythrocyte membrane fluidity as compared to resting time, but this was not accompanied by significant changes in the plasmatic MDA and 4-HDA concentrations. The highest erythrocyte membrane rigidity was detected immediately after strenu- ous exercise until exhaustion was performed. Protein car- bonyl levels were higher after exhaustive exercises than at rest. Continuous progressive and strenuous exercises until exhaustion, but not submaximal workload, resulted in a significant enhanced accumulation of carbonylated proteins in the plasma. These findings are consistent with the idea that exercise exaggerates oxidative damage, which may contribute, at least partially, to explain the rigidity in the membrane of the erythrocytes due to acute exercise. Keywords Acute exercise  Membrane fluidity  Lipid peroxidation  Protein oxidation  Erythrocyte Introduction Numerous processes in or among cells, including signal transduction, solute transport and cell–cell interaction, are membrane mediated (Derby and Gleeson 2007; Sudhahar et al. 2008). Cell membranes are complex bilayer structures compiled of a variety of lipids and proteins. According to the fluid-mosaic model proposed by Singer and Nicolson (1972), membrane lipids form a fluid bilayer where the incorporated proteins as well as the lipids themselves are free to diffuse laterally. Today, we are aware that both membrane structural intactness and adequate dynamics of the lipid bilayer are indispensable requirements for optimal functioning of cells (Stubbs and Smith 1984). Thus, mea- surements of the membrane fluidity reflect the biophysical and biochemical characteristics of the biological mem- branes and are an indicator of membrane function (Li et al. 1999). Over the last few decades, intensive research in the field of oxidative stress indicates that exercise exacerbates free Communicated by Susan Ward. C. Berzosa  E. M. Go´mez–Trulle´n  E. Piedrafita  I. Cebria´n  E. Martı ´nez–Balları ´n  F. J. Miana–Mena  L. Fuentes–Broto  J. J. Garcı ´a Aging Physiology and Oxidative Stress (B40), Universidad de Zaragoza, Saragossa, Spain J. J. Garcı ´a (&) Department of Pharmacology and Physiology, Faculty of Medicine, University of Zaragoza, c) Domingo Miral s/n, 50009 Saragossa, Spain e-mail: jjgarcia@unizar.es 123 Eur J Appl Physiol (2011) 111:1127–1133 DOI 10.1007/s00421-010-1738-6