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The Journal of Cell Biology, Vol 112, 711-718, Copyright © 1991 by The Rockefeller University Press
ARTICLES |
N Grandin and M Charbonneau
Laboratoire de Biologie et Genetique du Developpement, URA CNRS 256, Universite de Rennes I, France.
In Xenopus embryos, previous results failed to detect changes in the activity of free calcium ions (Ca2+i) during cell division using Ca2(+)- selective microelectrodes, while experiments with aequorin yielded uncertain results complicated by the variation during cell division of the aequorin concentration to cell volume ratio. We now report, using Ca2(+)-selective microelectrodes, that cell division in Xenopus embryos is accompanied by periodic oscillations of the Ca2+i level, which occur with a periodicity of 30 min, equal to that of the cell cycle. These Ca2+i oscillations were detected in 24 out of 35 experiments, and had a mean amplitude of 70 nM, around a basal Ca2+i level of 0.40 microM. Ca2+i oscillations did not take place in the absence of cell division, either in artificially activated eggs or in cleavage-blocked embryos. Therefore, Ca2+i oscillations do not represent, unlike intracellular pH oscillations (Grandin, N., and M. Charbonneau. J. Cell Biol. 111:523- 532. 1990), a component of the basic cell cycle ("cytoplasmic clock" or "master oscillator"), but appear to be more likely related to some events of mitosis.
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