Intracellular ca(2+) pools and fluxes in cardiac muscle-derived h9c2 cells.
Relevant Ca(2+) pools and fluxes in H9c2 cells have been studied using fluorescent indicators and Ca(2+)-mobilizing agents. Vasopressin produced a cytoplasmic Ca(2+) peak with half-maximal effective concentration of 6 nM, whereas thapsigargin-induced Ca(2+) increase showed half-maximal effect at 3 nM. Depolarization of the mitochondrial inner membrane by protonophore was also associated with an increase in cytoplasmic Ca(2+). Ionomycin induced a small and sustained depolarization, while thapsigargin had a small but transient effect. The thapsigargin-sensitive Ca(2+) pool was also sensitive to ionomycin, whereas the protonophore-sensitive Ca(2+) pool was not. The vasopressin-induced cytoplasmic Ca(2+) signal, which caused a reversible discharge of the sarco-endoplasmic reticulum Ca(2+) pool, was sensed as a mitochondrial Ca(2+) peak but was unaffected by the permeability transition pore inhibitor cyclosporin A. The mitochondrial Ca(2+) peak was affected by cyclosporin A when the Ca(2+) signal was induced by irreversible discharge of the intracellular Ca(2+) pool, i.e., adding thapsigargin. These observations indicate that the mitochondria interpret the cytoplasmic Ca(2+) signals generated in the reticular store.
Lax
Antonio
A
Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Universidad de Murcia, Murcia, Spain.
Soler
Fernando
F
Fernández-Belda
Francisco
F
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006321:Heart / Q000187:drug effects; D007425:Intracellular Membranes / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018613:Microscopy, Confocal; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D019284:Thapsigargin / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology
D005456:Fluorescent Dyes; D014667:Vasopressins; D019284:Thapsigargin; D002118:Calcium; D016257:Fura-2