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Sodium withdrawal contractures in developing and regenerating rat extensor digitorum longus muscles
1Laboratory of Cellular and Molecular Physiopathology and Pharmacology, CJF Inserm 96-01, CHR G.R. Laennec, Nantes, France.
Insights
Sodium withdrawal contractures in extensor digitorum longus (EDL) muscles occur in early development and in regenerating muscle. Denervation appears crucial for these contractures, possibly involving calcium-sodium exchange.
Area of Science:
- Muscle physiology
- Developmental biology
- Regenerative medicine
Background:
- Sodium withdrawal contractures are observed in developing extensor digitorum longus (EDL) muscles within the first 6 days post-birth.
- These contractures are absent in mature EDL muscles.
- Regenerating EDL muscles exhibit unique responses to sodium withdrawal.
Purpose of the Study:
- To investigate the occurrence and timing of zero-sodium (zero-Na) contractures in regenerating EDL muscles.
- To explore the role of denervation in the development of these contractures.
- To propose a mechanism for zero-Na contractures in regenerating muscle.
Main Methods:
- Induction of muscle regeneration using bupivacaine injection.
- Muscle autotransplantation procedures.
- Intervention on sliced muscles.
- Observation of zero-Na contractures at various time points post-intervention.
Main Results:
- Zero-Na contractures were observed 7 days after bupivacaine injection but not at later time points (14 or 90 days).
- Regenerating EDL muscles showed zero-Na contractures 7, 14, and 90 days after autotransplantation.
- Sliced muscles also exhibited zero-Na contractures at 7, 14, and 90 days post-intervention.
- These contractures were linked to denervation in regenerating muscles.
Conclusions:
- Denervation plays a significant role in the development of zero-Na contractures in regenerating muscles.
- A calcium-sodium exchange mechanism across the sarcolemma is suggested as a potential cause for these contractures in regenerating muscle.
Abstract:
During postnatal development of extensor digitorum longus (EDL) muscle, sodium withdrawal contractures were observed during the first 6 days after birth, and not after this time. In regenerating EDL muscles, zero-Na contractures were demonstrated: (1) 7 days after bupivacaine injection, but not 14 or 90 days after this injection; (2) 7, 14, and 90 days after autotransplantation; and (3) 7, 14, and 90 days after the intervention in sliced muscles. The present findings emphasize the role of the denervation in the development of zero-Na contractures in the regenerating muscles and suggest that a calcium-sodium exchange across the sarcolemma may appear in these muscles.