2-D electrophoresis was used to investigate the effects of a quantitative trait locus for muscle hypertrophy on sarcoplasmic protein expression in ovine muscles. In the Belgian Texel breed, the QTL for muscle hypertrophy is localized in the chromosomal region of the myostatin-encoding gene. Based on microsatellite markers flanking the myostatin gene, we compared the hypertrophied genotype with the normal genotype. The average age of animals was three months. Among the four muscles studied, in hypertrophied genotype only the vastus medialis was normal, whereas the others - semimembranosus, tensor fasciae latae and longissimus dorsi - were hypertrophied. In the hypertrophied genotype, these muscles showed up-regulation of enzymes involved in glycolytic metabolisms together with oxidative metabolism in longissimus dorsi muscle. Certain chaperone proteins including glutathione S-transferase- Pi, heat shock protein-27, and heat shock cognate-70 were also more highly expressed, probably due to increased use of energetic pathways. Expression of the iron transport protein transferrin was increased. Alpha-1-antitrypsin was the only protein showing a similar pattern of expression (i.e. less expressed) in all four muscles of the hypertrophied genotype. It is suggested that transferrin and alpha-1-antitrypsin may interact to reinforce myogenic proliferative signalling. ; La mutation Texel Belge induit une hypertrophie musculaire. Elle affecte le gène codant pour la myostatine et touche l'ensemble de la musculature. Toutefois les mécanismes physiologiques et biochimiques sous-jacents ne sont pas encore élucidés. Notre étude est axée sur la fraction sarcoplasmique du protéome dans laquelle se trouvent les protéines du métabolisme et des voies de transduction. L'étude comparative en gels d'électrophorèse 2D porte sur des muscles d'homozygotes Texel et d'homozygotes Romanov au locus. En comparant des muscles aux compositions variées et présentant divers degrés de développement, nous avons montré qu'il existait des variations ...