Key result
Cross-innervation of rabbit soleus and extensor digitorum longus muscles changed the relative proportions of alpha, gamma, and delta tropomyosin subunits as expected from the change in speed.
Why the study?
Does cross-innervation alter the tropomyosin composition in rabbit skeletal muscle?
Does cross-innervation alter the tropomyosin composition in rabbit skeletal muscle?
Cross-innervation of rabbit skeletal muscle alters the relative proportions of alpha, gamma, and delta tropomyosin subunits corresponding to changes in muscle speed, while the beta subunit fraction remains constant.
Answers are grounded in this paper and cite their sources.
Hypothesis-generating for neural control of sarcomeric proteins in mammals; leaves open relevance to human muscle or cardiac disease.
Soleus, semitendinosus and crureus muscles of the rabbit were found to contain alpha- and beta-tropomyosin subunits and additional forms that have been provisionally designated gamma and delta. Extensor digitorum longus and psoas muscles contained only alpha and beta subunits, the relative proportions of which varied between single fibres of psoas muscle. On cross-innervation of rabbit soleus and extensor digitorum longus muscles, the fraction of the total tropomyosin present as the beta subunit remained constant. The relative proportions of alpha, gamma and delta subunits changed as would be expected from the change in speed that occurred.
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Heeley et al. (1983) studied this question. Cross-innervation vs. Normal innervation was evaluated on Tropomyosin composition (alpha, beta, gamma, and delta subunits). Cross-innervation of rabbit soleus and extensor digitorum longus muscles changed the relative proportions of alpha, gamma, and delta tropomyosin subunits as expected from the change in speed.
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