Analysis of puff dynamics in oocytes: interdependence of puff amplitude and inter-puff interval

¹ Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
² University of California, Irvine

^* To whom correspondence should be addressed. E-mail: dfraiman{at}df.uba.ar.

Submitted on October 13, 2005
Revised on November 28, 2005
Accepted on 10 February 2006

	Abstract

Puffs are localized Ca²⁺ signals that arise in oocytes in response to inositol 1,4,5-trisphosphate (IP₃). They are analogous to the sparks of myocytes and are believed to be the result of the liberation of Ca²⁺ from the endoplasmic reticulum through the coordinated opening of IP₃-receptor/channels clustered at a functional release site. In this paper 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 inter-puff 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 Ca²⁺ that is liberated during puffs. We construct a stochastic model for a cluster of IP₃-receptor/ channels that quantitatively replicates the observed behavior, and determine that the characteristic time for a channel to escape from the inhibitory state is of the order of seconds.

Key Words: calcium dynamics, calcium puffs, inositol trisphosphate receptor