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>Length‐dependence of isometric twitch tension potentiation and myosin phosphorylation in mouse skeletal muscle
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Length‐dependence of isometric twitch tension potentiation and myosin phosphorylation in mouse skeletal muscle
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机译：Length‐dependence of isometric twitch tension potentiation and myosin phosphorylation in mouse skeletal muscle
AbstractThe effect of changes in muscle length on post‐tetanic isometric twitch tension potentiation and myosin P‐light chain phosphorylation‐was studied at 23°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 L0to 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 phosphor‐ylation. Net myosin phosphorylalion measured after a 1.5 s tetanus at 1.23 L0is 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 a
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