title: Relationship between intracellular calcium concentration and relaxation of rat fast and slow muscles.
abstract: Following injection of aequorin into small bundles of rat soleus and extensor digitorum longus muscles, simultaneous measurements of light (proportional to the intracellular free calcium ion concentration ([Ca2+]i)) and force were recorded during muscle twitches over a range of temperatures from 10 to 37 degrees C. The Arrhenius plots for rate of decline of [Ca2+]i following a twitch were linear and yielded the same activation enthalpy (Ea) for both muscle types, indicating that the same process controls Ca2+ uptake in both fast and slow muscles. Arrhenius plots of force decay rate constants showed a break around 20 to 25 degrees C with the Ea's above the break being similar to the Ea's for decline of [Ca2+]i and indicating a close relationship between rate of relaxation and decline of [CA2+]i above this temperature.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D066298:In Vitro Techniques; D009119:Muscle Contraction; D009126:Muscle Relaxation; D009928:Organ Specificity; D051381:Rats; D011919:Rats, Inbred Strains; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013696:Temperature
chemical_list: D002118:Calcium