Effects of vigorous isometric muscle contraction on titin stiffness-related contractile properties in rat fast-twitch muscles.
Am J Physiol Regul Integr Comp Physiol
; 321(6): R858-R868, 2021 12 01.
Article
em En
| MEDLINE
| ID: mdl-34668430
ABSTRACT
This study was conducted to examine the effects of an acute bout of vigorous isometric contractions on titin stiffness-related contractile properties in rat fast-twitch skeletal muscles. Intact gastrocnemius muscles were electrically stimulated in situ until the force was reduced to â¼50% of the initial force. Immediately after cessation of the stimulation, the superficial regions of the muscles were dissected and subjected to biochemical and skinned fiber analyses. The stimulation resulted in a decrease in the titin-based passive force. The amounts of fragmented titin were unchanged by the stimulation. Protein kinase Cα-treatment increased the passive force in stimulated fibers to resting levels. The stimulation had no effect on the maximum Ca2+-activated force (max Ca2+ force) at a sarcomere length (SL) of 2.4 µm and decreased myofibrillar (my)-Ca2+ sensitivity at 2.6-µm SL. Stretching the SL to 3.0 µm led to the augmentation of the max Ca2+ force and my-Ca2+ sensitivity in both rested and stimulated fibers. For the max Ca2+ force, the extent of the increase was smaller in stimulated than in rested fibers, whereas for my-Ca2+ sensitivity, it was higher in stimulated than in rested fibers. These results suggest that vigorous isometric contractions decrease the titin-based passive force, possibly because of a reduction in phosphorylation by protein kinase Cα, and that the decreased titin stiffness may contribute, at least in part, to muscle fatigue.
Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Fibras Musculares de Contração Rápida
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Fadiga Muscular
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Conectina
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Contração Isométrica
Limite:
Animals
Idioma:
En
Revista:
Am J Physiol Regul Integr Comp Physiol
Assunto da revista:
FISIOLOGIA
Ano de publicação:
2021
Tipo de documento:
Article
País de afiliação:
Japão