Force enhancement after stretch in mammalian muscle fiber: no evidence of cross-bridge involvement.
Am J Physiol Cell Physiol
; 307(12): C1123-9, 2014 Dec 15.
Article
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| MEDLINE
| ID: mdl-25298425
ABSTRACT
Stretching of activated skeletal muscles induces a force increase above the isometric level persisting after stretch, known as residual force enhancement (RFE). RFE has been extensively studied; nevertheless, its mechanism remains debated. Unlike previous RFE studies, here the excess of force after stretch, termed static tension (ST), was investigated with fast stretches (amplitude 3-4% sarcomere length; duration 0.6 ms) applied at low tension during the tetanus rise in fiber bundles from flexor digitorum brevis (FDB) mouse muscle at 30°C. ST was measured at sarcomere length between 2.6 and 4.4 µm in normal and N-benzyl-p-toluene sulphonamide (BTS)-added (10 µM) Tyrode solution. The results showed that ST has the same characteristics and it is equivalent to RFE. ST increased with sarcomere length, reached a peak at 3.5 µm, and decreased to zero at â¼4.5 µm. At 4 µm, where active force was zero, ST was still 50% of maximum. BTS reduced force by â¼75% but had almost no effect on ST. Following stimulation, ST developed earlier than force, with a time course similar to internal Ca(2+) concentration it was present 1 ms after the stimulus, at zero active force, and peaked at â¼3-ms delay. At 2.7 µm, activation increased the passive sarcomere stiffness by a factor of â¼7 compared with the relaxed state All our data indicate that ST, or RFE, is independent of the cross-bridge presence and it is due to the Ca(2+)-induced stiffening of a sarcomeric structure identifiable with titin.
Palabras clave
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Reflejo de Estiramiento
/
Fibras Musculares Esqueléticas
/
Fuerza Muscular
/
Contracción Muscular
Tipo de estudio:
Prognostic_studies
Límite:
Animals
Idioma:
En
Revista:
Am J Physiol Cell Physiol
Asunto de la revista:
FISIOLOGIA
Año:
2014
Tipo del documento:
Article
País de afiliación:
Italia