Influence of fiber type and muscle source on Ca2+ sensitivity of rat fibers.
This study investigated the influence of muscle source and fiber type on the calcium sensitivity of skinned rat skeletal muscle fibers from predominantly slow muscles [soleus (SOL) and adductor longus (AL)], mixed muscle [posterior gracilis (PG)], and predominantly fast-twitch muscle [extensor digitorum longus (EDL)]. Fibers were characterized histochemically and by one-dimensional protein gel electrophoresis, and calcium-tension relationships were determined. Fiber type and muscle source had significant effects on the negative log of the calcium concentration associated with half-maximal tension (pCa1/2). Slow-twitch fibers had larger values of pCa1/2 than did fast-twitch fibers. Slow-twitch fibers from the predominantly slow muscles, SOL and AL, had similar values of pCa1/2 but slightly smaller values than from the mixed muscle, PG. Fast-glycolytic (FG) fibers from the predominantly fast muscle, EDL, had a higher pCa1/2 than fibers from the mixed fiber type muscle, PG. There were no differences between the pCa1/2 associated with FG and fast-oxidative-glycolytic fibers.
Laszewski-Williams
B
B
Department of Physiology, University of Washington, Seattle 98195.
Ruff
R L
RL
Gordon
A M
AM
D000251:Adenosine Triphosphatases / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D006019:Glycolysis; D009119:Muscle Contraction / Q000187:drug effects*; D009124:Muscle Proteins / Q000032:analysis; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D009928:Organ Specificity; D051381:Rats; D011919:Rats, Inbred Strains; D012518:Sarcomeres / Q000502:physiology; D013385:Succinate Dehydrogenase / Q000032:analysis
D009124:Muscle Proteins; D013385:Succinate Dehydrogenase; D000251:Adenosine Triphosphatases; D002118:Calcium