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Maximal shortening velocities, isomyosins and fibre types in soleus muscle of mice, rats and guinea‐pigs.
Author(s) -
Asmussen G,
Maréchal G
Publication year - 1989
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1989.sp017758
Subject(s) - soleus muscle , guinea pig , chemistry , medicine , biophysics , endocrinology , anatomy , biology , skeletal muscle
1. Guinea‐pig soleus contains only type I fibres and slow isomyosin, SM2. Rat and mouse soleus contain about 70% of type I fibres and a mixture of isomyosins: slow, SM2 and intermediate, IM. Many rat soleus muscles contain a third isomyosin of a slow type, SM1. 2. The maximal velocity of unloaded shortening, V0, is largest in mouse soleus (6.11 Lf s‐1), slowest in guinea‐pig soleus (1.67 Lf s‐1) and intermediate in rat soleus (4.16 Lf s‐1) (Lf = fibre length). 3. In guinea‐pig soleus, V0 is equal to the maximal velocity (Vmax) computed using the Hill force‐velocity relationship; V0 is approximately twice as large as Vmax in mouse and rat soleus. 4. V0 measures the unloaded shortening velocity of the fastest fibres whereas Vmax is a function of the force‐velocity characteristics of all the fibres contained in the muscle. 5. V0 increases according to the isomyosin composition of the fibres in the sequence SM2 less than SM1 + IM less than IM.