Halothane-induced intracellular calcium release in cholinergic cells.
Low concentrations of halothane and isoflurane can release acetylcholine in an extracellular Ca(2+)-independent manner. In the present study, a cholinergic cell line (SN56) was used to examine whether release of calcium from intracellular stores occurs in the presence of halothane. Changes in intracellular calcium concentration ([Ca(2+)](i)) were measured using fluo-3, a fluorescent calcium-sensitive dye and laser scanning confocal microscopy. Halothane, at sub-anesthetic concentrations (14, 28, 40 and 56 microM), increased [Ca(2+)](i) in SN56 cells. This effect remained even when the cells were perfused with medium lacking extracellular calcium, suggesting the involvement of intracellular Ca(2+) sources. SN56 cells responded to ryanodine by increasing [Ca(2+)](i) and this effect was blocked by dantrolene, an inhibitor of Ca(2+)-release from ryanodine-sensitive stores. The effect of halothane was attenuated after the increase in [Ca(2+)](i) induced by ryanodine and it was suppressed by dantrolene, suggesting the participation of ryanodine-sensitive stores. Using cyclopiazonic acid, a Ca(2+)-ATPase inhibitor, we investigated whether the depletion of intracellular Ca(2+) stores interfered with the effect of halothane. Cyclopiazonic acid significantly decreased the increase in [Ca(2+)](i) induced by the volatile anesthetic. It is suggested that sub-anesthetic concentrations of halothane may increase [Ca(2+)](i) by releasing Ca(2+) from intracellular stores in cholinergic cells.
Gomez
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RS
Departamento de Cirurgia, Faculdade de Medicina da UFMG, Avenida Alfredo Balena, 190, CEP 30130-100,Belo Horizonte, Minas Gerais, Brazil. renatogomez@ig.com.br
Guatimosim
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C
Barbosa
J
J
Massensini
A R
AR
Gomez
M V
MV
Prado
M A
MA
D000109:Acetylcholine / Q000378:metabolism*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000814:Aniline Compounds; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000172:deficiency; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002478:Cells, Cultured; D003620:Dantrolene / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005456:Fluorescent Dyes; D006221:Halothane / Q000494:pharmacology*; D006801:Humans; D007424:Intracellular Fluid / Q000187:drug effects* / Q000378:metabolism; D018613:Microscopy, Confocal; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014966:Xanthenes
D018685:Anesthetics, Inhalation; D000814:Aniline Compounds; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D009125:Muscle Relaxants, Central; D019837:Ryanodine Receptor Calcium Release Channel; D014966:Xanthenes; D012433:Ryanodine; C059715:Fluo-3; D011189:Potassium Chloride; D000252:Calcium-Transporting ATPases; D003620:Dantrolene; D000109:Acetylcholine; D002118:Calcium; D006221:Halothane