title: Luminal Ca(2+) dynamics during IP3R mediated signals.
abstract: The role of cytosolic Ca(2+) on the kinetics of Inositol 1,4,5-triphosphate receptors (IP3Rs) and on the dynamics of IP3R-mediated Ca(2+) signals has been studied at large both experimentally and by modeling. The role of luminal Ca(2+) has not been investigated with that much detail although it has been found that it is relevant for signal termination in the case of Ca(2+) release through ryanodine receptors. In this work we present the results of observing the dynamics of luminal and cytosolic Ca(2+) simultaneously in Xenopus laevis oocytes. Combining observations and modeling we conclude that there is a rapid mechanism that guarantees the availability of free Ca(2+) in the lumen even when a relatively large Ca(2+) release is evoked. Comparing the dynamics of cytosolic and luminal Ca(2+) during a release, we estimate that they are consistent with a 80% of luminal Ca(2+) being buffered. The rapid availability of free luminal Ca(2+) correlates with the observation that the lumen occupies a considerable volume in several regions across the images.
authors.affiliation: DF, FCEN-UBA, Argentina. IFIBA, CONICET, Argentina.
authors.forename: Lucia F
authors.initials: LF
authors.lastname: Lopez
authors.forename: Silvina Ponce
authors.initials: SP
authors.lastname: Dawson
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D003600:Cytosol / Q000378:metabolism; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D002118:Calcium