Effect of mitochondria poisoning by FCCP on Ca2+ signaling in mouse skeletal muscle fibers.
We have studied the effects of mitochondria poisoning by carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) on Ca(2+) signaling in enzymatically dissociated mouse flexor digitorum brevis (FDB) muscle fibers. We used Fura-2AM to measure resting [Ca(2+)](i) and MagFluo-4AM to measure Ca(2+) transients. Exposure to FCCP (2 microM, 2 min) caused a continuous increase in [Ca(2+)](i) at a rate of 0.60 nM/s and a drastic reduction of electrically elicited Ca(2+) transients without much effect on their decay phase. Half of the maximal effect occurred at [Ca(2+)](i) = 220 nM. This effect was partially reversible after long recuperation and was not diminished by Tiron, a reactive oxygen species (ROS) scavenger. FCCP had no effects on fiber excitability as shown by the generation of action potentials. 4CmC, an agonist of ryanodine receptors, induced a massive Ca(2+) release. FCCP diminished the rate but not the amount of Ca(2+) released, indicating that depletion of Ca(2+) stores did not cause the decrease in Ca(2+) transient amplitude. Ca(2+) transient amplitude could also be diminished, but to a lesser degree, by increases in [Ca(2+)](i) induced by repetitive stimulation of fibers treated with ciclopiazonic acid. This suggests an important role for Ca(2+) in the FCCP effect on transient amplitude.
Laboratorio de Fisiología Celular, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Cientificas, Apartado 21827, Caracas 1020A, Venezuela. ccaputo@ivic.ve
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D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt / Q000494:pharmacology; D000200:Action Potentials; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000633:toxicity*; D003408:Cresols / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D016166:Free Radical Scavengers / Q000494:pharmacology; D016257:Fura-2 / Q000031:analogs & derivatives; D007211:Indoles / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D008856:Microscopy, Fluorescence / Q000379:methods; D008931:Mitochondria, Muscle / Q000187:drug effects* / Q000378:metabolism; D018656:Muscle Fibers, Fast-Twitch / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D014475:Uncoupling Agents / Q000633:toxicity*
D003408:Cresols; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D016166:Free Radical Scavengers; D007211:Indoles; D019837:Ryanodine Receptor Calcium Release Channel; D014475:Uncoupling Agents; C049925:fura-2-am; C006984:chlorocresol; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D000252:Calcium-Transporting ATPases; D016257:Fura-2; C000543:cyclopiazonic acid