Analysis of puff dynamics in oocytes: interdependence of puff amplitude and interpuff interval.
Puffs are localized Ca(2+) signals that arise in oocytes in response to inositol 1,4,5-trisphosphate (IP(3)). They are analogous to the sparks of myocytes and are believed to be the result of the liberation of Ca(2+) from the endoplasmic reticulum through the coordinated opening of IP(3) receptor/channels clustered at a functional release site. In this article, we analyze sequences of puffs that occur at the same site to help elucidate the mechanisms underlying puff dynamics. In particular, we show a dependence of the interpuff time on the amplitude of the preceding puff, and of the amplitude of the following puff on the preceding interval. These relationships can be accounted for by an inhibitory role of the Ca(2+) that is liberated during puffs. We construct a stochastic model for a cluster of IP(3) receptor/channels that quantitatively replicates the observed behavior, and we determine that the characteristic time for a channel to escape from the inhibitory state is of the order of seconds.
Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina. dfraiman@df.uba.ar
Daniel
D
Fraiman
Bernardo
B
Pando
Sheila
S
Dargan
Ian
I
Parker
Silvina Ponce
SP
Dawson
D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000737:chemistry / Q000502:physiology; D020013:Calcium Signaling / Q000502:physiology*; D003600:Cytosol / Q000378:metabolism; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018613:Microscopy, Confocal; D008954:Models, Biological; D009865:Oocytes / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000502:physiology; D016008:Statistical Distributions; D013269:Stochastic Processes; D014982:Xenopus laevis
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D002118:Calcium