Length-dependence of isometric twitch tension potentiation and myosin phosphorylation in mouse skeletal muscle.
J Cell Physiol
; 143(2): 257-62, 1990 May.
Article
em En
| MEDLINE
| ID: mdl-2332450
ABSTRACT
The effect of changes in muscle length on post-tetanic isometric twitch tension potentiation and myosin P-light chain phosphorylation was studied at 23 degrees C in the mouse extensor digitorum longus muscle. The length-tension relationship was determined for the same muscles after a 30 min period of quiescence and between 30 s and 3 min after a 1.5 s tetanus at L0. Isometric twitch tension is increased at all muscle lengths after the tetanus; however, the fractional increase in twitch tension rises from 0.2 at L0 to a maximum of 0.3 at 1.2 L0. The fractional increase in twitch tension measured at any fixed muscle length is constant between 30 s and 3 min post-tetanus. P-light chain phosphorylation remains constant between 30 s and 3 min post-tetanus followed by a slow decline to basal values. Under fixed length conditions, there is linear relationship between the relative magnitude of the twitch tension and the extent of P-light chain phosphorylation. Net myosin phosphorylation measured after a 1.5 s tetanus at 1.23 L0 is 35% less than that obtained under the same conditions at L0. Thus, contraction-induced phosphorylation of P-light chain decreases with increased muscle length and post-tetanic potentiation at a constant level of P-light chain phosphorylation increases with increasing muscle length. These observations may be consistent with alterations in the sarcoplasmic Ca2+ ion transient as the muscle is lengthened.
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Base de dados:
MEDLINE
Assunto principal:
Miosinas
/
Contração Muscular
/
Músculos
Limite:
Animals
Idioma:
En
Ano de publicação:
1990
Tipo de documento:
Article