Analysis of Puff Dynamics in Oocytes: Interdependence of Puff Amplitude and Interpuff Interval

• Published in: Biophysical journal Vol. 90; no. 11; pp. 3897 - 3907
• Main Authors: Fraiman, Daniel, Pando, Bernardo, Dargan, Sheila, Parker, Ian, Dawson, Silvina Ponce
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.06.2006; Biophysical Society
• Subjects: Animal care; Animals; Binding Sites; Biophysical Theory and Modeling; Calcium - physiology; Calcium Channels - chemistry; Calcium Channels - physiology; Calcium Signaling - physiology; Cytosol - metabolism; Fluorescence; In Vitro Techniques; Inositol 1,4,5-Trisphosphate Receptors; Microscopy, Confocal; Models, Biological; Oocytes - physiology; Receptors, Cytoplasmic and Nuclear - chemistry; Receptors, Cytoplasmic and Nuclear - physiology; Statistical Distributions; Stochastic Processes; Xenopus laevis
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1529/biophysj.105.075911

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.