Force produced after stretch in sarcomeres and half-sarcomeres isolated from skeletal muscles

• DOI: 10.1038/srep02320
• Publication Date: 2013-07-31T09:05:50Z
• Authors: Fábio C. Minozzo; Bruno M. Baroni; José A. Correa; Marco A. Vaz; Dilson E. Rassier
• Keywords: Sarcomeres; 0301 basic medicine; Molecular Mechanisms of Muscle Regeneration and Atrophy; Biomedical Engineering; Skeletal muscle; FOS: Medical engineering; Article; 03 medical and health sciences; Engineering; Elastic Modulus; Isometric Contraction; Physical Stimulation; Biochemistry, Genetics and Molecular Biology; Health Sciences; Animals; Molecular Biology; Biology; Internal medicine; Cells, Cultured; Life Sciences; Diagnosis and Management of Hypertrophic Cardiomyopathy; Sarcomere; Musculoskeletal Modeling; Analysis of Electromyography Signal Processing; Physical Sciences; Myocyte; Medicine; Rabbits; Stress, Mechanical; Anatomy; Cardiology and Cardiovascular Medicine

AbstractThe goal of this study was to evaluate if isolated sarcomeres and half-sarcomeres produce a long-lasting increase in force after a stretch is imposed during activation. Single and half-sarcomeres were isolated from myofibrils using micro-needles, which were also used for force measurements. After full force development, both preparations were stretched by different magnitudes. The sarcomere length (SL) or half-sarcomere length variations (HSL) were extracted by measuring the initial and final distances from the Z-line to the adjacent Z-line or to a region externally adjacent to the M-line of the sarcomere, respectively. Half-sarcomeres generated approximately the same amount of isometric force (29.0 ± SD 15.5 nN·μm−2) as single sarcomeres (32.1 ± SD 15.3 nN·μm−2) when activated. In both cases, the steady-state forces after stretch were higher than the forces during isometric contractions at similar conditions. The results suggest that stretch-induced force enhancement is partly caused by proteins within the half-sarcomere.