Structure-function relationship of soleus muscle fibres from the rhesus monkey.
Functional and structural properties of rhesus monkey skinned fibres were studied in order to examine the relationship between calcium/strontium (Ca/Sr) activation characteristics and protein composition. The fibres were classified according to their Ca/Sr affinity into slow (61%) and fast groups (39%). According to the myosin isoform composition, two additional hybrid types were defined. Thus, four profiles were characterized: two corresponding to slow (S) and fast (F) isoforms and two corresponding to a mixed proportion of slow and fast isoforms. They were called hybrid slow (HS) or hybrid fast (HF) based on the predominant myosin isoform. Tension/pCa parameters and maximal shortening velocities were determined. S fibres showed a higher pCa threshold and affinity as well as shallower slopes of their tension/pCa curve than did F fibres. HS and HF fibres exhibited tension/pCa curves which were positioned close to those of S and F fibres, respectively. No significant difference was observed between S and HS fibres or between F and HF fibres. Maximal shortening velocity values were higher for fibres expressing predominantly fast myosin isoforms. We suggest than when both S and F isoforms of myofibrillar proteins are expressed in a muscle fibre, the functional properties are mainly governed by the predominant isoform.
Cordonnier
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C
Laboratoire de Physiologie des Structures Contractiles, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France.
Stevens
L
L
Picquet
F
F
Mounier
Y
Y
D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D066298:In Vitro Techniques; D007536:Isomerism; D008253:Macaca mulatta; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000502:physiology; D009124:Muscle Proteins / Q000032:analysis; D018482:Muscle, Skeletal / Q000737:chemistry / Q000502:physiology*; D009210:Myofibrils / Q000737:chemistry / Q000502:physiology; D009218:Myosins / Q000032:analysis; D013324:Strontium / Q000737:chemistry; D013329:Structure-Activity Relationship
D009124:Muscle Proteins; D009218:Myosins; D002118:Calcium; D013324:Strontium