Quantifying calcium fluxes underlying calcium puffs in Xenopus laevis oocytes
We determine the calcium fluxes through inositol 1,4,5-trisphosphate receptor/channels underlying calcium puffs of Xenopus laevis oocytes using a simplified version of the algorithm of Ventura et al. [1]. An analysis of 130 puffs obtained with Fluo-4 indicates that Ca2+ release comes from a region o...
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| Autores principales: | , , , |
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2010
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_01434160_v47_n3_p273_Bruno http://hdl.handle.net/20.500.12110/paper_01434160_v47_n3_p273_Bruno |
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| Sumario: | We determine the calcium fluxes through inositol 1,4,5-trisphosphate receptor/channels underlying calcium puffs of Xenopus laevis oocytes using a simplified version of the algorithm of Ventura et al. [1]. An analysis of 130 puffs obtained with Fluo-4 indicates that Ca2+ release comes from a region of width ∼450 nm, that the release duration is peaked around 18 ms and that the underlying Ca2+ currents range between 0.12 and 0.95 pA. All these parameters are independent of IP3 concentration. We explore what distributions of channels that open during a puff, Np, and what relations between current and number of open channels, I(Np), are compatible with our findings and with the distribution of puff-to-trigger amplitude ratio reported in Rose et al. [2]. To this end, we use simple "mean field" models in which all channels open and close simultaneously. We find that the variability among clusters plays an important role in shaping the observed puff amplitude distribution and that a model for which I(Np) ∼ Np for small Np and I (Np) ∼ Np 1 / α (α > 1) for large Np, provides the best agreement. Simulations of more detailed models in which channels open and close stochastically show that this nonlinear behavior can be attributed to the limited time resolution of the observations and to the averaging procedure that is implicit in the mean-field models. These conclusions are also compatible with observations of ∼400 puffs obtained using the dye Oregon green. © 2009 Elsevier Ltd. All rights reserved. |
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