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Location of the initiation site of calcium transients and sparks in rabbit heart Purkinje cells

Cordeiro, J. M. ; Spitzer, K. W. ; Giles, W. R. ; Ershler, P. E. ; Cannell, M. B. ; Bridge, J. H. B.

The Journal of physiology, 2001-03, Vol.531 (2), p.301-314 [Periódico revisado por pares]

Oxford, UK: The Physiological Society

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  • Título:
    Location of the initiation site of calcium transients and sparks in rabbit heart Purkinje cells
  • Autor: Cordeiro, J. M. ; Spitzer, K. W. ; Giles, W. R. ; Ershler, P. E. ; Cannell, M. B. ; Bridge, J. H. B.
  • Assuntos: Animals ; Biological Transport ; Calcium - physiology ; Computer Simulation ; Electric Stimulation ; Heart - physiology ; Models, Cardiovascular ; Myocardium - cytology ; Original ; Purkinje Cells - cytology ; Purkinje Cells - physiology ; Rabbits ; Tissue Distribution
  • É parte de: The Journal of physiology, 2001-03, Vol.531 (2), p.301-314
  • Notas: ObjectType-Article-1
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  • Descrição: The distribution and localization of Ca 2+ transients and Ca 2+ sparks in isolated adult rabbit Purkinje cells were examined using confocal microscopy and the Ca 2+ indicator fluo-3. When cells were field stimulated in 2.0 m m Ca 2+ buffer, a transverse confocal line scan (500 Hz) showed that the fluorescence intensity was greatest at the cell periphery during the onset of the Ca 2+ transient ([Ca 2+ ] i ). In contrast, the [Ca 2+ ] i of ventricular cells showed a more uniform pattern of activation across the cell. Staining with di-8-ANEPPS revealed that Purkinje cells lack t-tubules, whereas ventricular cells have an extensive t-tubular system. When we superfused both cell types with a buffer containing 5 m m Ca 2+ -1 μ m isoproterenol (isoprenaline) they produced Ca 2+ sparks spontaneously. Ca 2+ sparks occurred only at the periphery of Purkinje cells but occurred throughout ventricular cells. Sparks in both cell types could be completely abolished by addition of the SR inhibitor thapsigargin (500 n m ). Brief exposure to nifedipine (10 μ m ) did not reduce the number of spontaneous sparks. Immunofluorescence staining of Purkinje cells with anti-ryanodine antibody revealed that ryanodine receptors (RyRs) are present at both peripheral and central locations. Computer simulations of experiments in which the calcium transient was evoked by voltage clamp depolarizations suggested that the increase in calcium observed in the centre of the cell could be explained by simple buffered diffusion of calcium. These computations suggested that the RyRs deep within the cell do not contribute significantly to the calcium transient. These results provide the first detailed, spatially resolved data describing Ca 2+ transients and Ca 2+ sparks in rabbit cardiac Purkinje cells. Both types of events are initiated only at subsarcolemmal SR Ca 2+ release sites suggesting that in Purkinje cells, Ca 2+ sparks only originate where the sarcolemma and sarcoplasmic reticulum form junctions. The role of the centrally located RyRs remains unclear. It is possible that because of the lack of t-tubules these RyRs do not experience a sufficiently large Ca 2+ trigger during excitation-contraction (E-C) coupling to become active.
  • Editor: Oxford, UK: The Physiological Society
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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