Halothane cooling contractures of skinned mammalian muscle fibers.
The effects of halothane or cooling on Ca2(+)-activated tensions and on the uptake and release of Ca2+ by the sarcoplasmic reticulum were investigated in chemically skinned fibers of the extensor digitorum longus muscle of adult rabbits. At 22 degrees C, halothane (greater than 0.46 mM) induced Ca2+ release from the SR of Ca2(+)-loaded skinned fibers that resulted in transient tensions. Higher concentrations of halothane (greater than 4.65 mM) reduced the steady-state accumulation of Ca2+ in the SR at 22 degrees C. Cooling (to less than 10 degrees C) elicited transient contractures (cooling-induced contractures [CC]) in Ca2(+)-loaded skinned fibers, despite the fact that the tensions elicited by adding Ca2+ to the bath were depressed at these low temperatures. The skinned fibers did not develop CCs at 12-16 degrees C. Halothane cooling contractures could be elicited at these temperatures by exposing the fibers to halothane concentrations that failed to elicit Ca2+ release at 22 degrees C. The halothane cooling contractures were blocked by procaine but not by lidocaine. It was concluded that these contractures resulted from a synergistic interaction between halothane and cooling that stimulates Ca2+ release from, and reduces Ca2+ uptake by, the sarcoplasmic reticulum.
Sudo
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RT
Departamento de Farmacologia Básica e Clínica, Universidade Federal do Rio de Janeiro, Brazil.
Zapata-Sudo
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Suarez-Kurtz
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D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003080:Cold Temperature; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D008012:Lidocaine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009132:Muscles / Q000378:metabolism / Q000648:ultrastructure; D011343:Procaine / Q000494:pharmacology; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism / Q000502:physiology
D002110:Caffeine; D011343:Procaine; D008012:Lidocaine; D002118:Calcium; D006221:Halothane