Changes in intracellular free calcium activity in Xenopus eggs following imposed intracellular pH changes using weak acids and weak bases. - Université Clermont Auvergne Accéder directement au contenu
Article Dans Une Revue BBA - Biochimica et Biophysica Acta Année : 1991

Changes in intracellular free calcium activity in Xenopus eggs following imposed intracellular pH changes using weak acids and weak bases.

Résumé

The aim of this work was to determine the potential relationships between rises in intracellular pH (pHi) and intracellular free calcium activity (Cai2+) during cell activation in Xenopus eggs. To do this, we used two weak bases, NH4Cl and procaine, and a weak acid, CO2, and measured Cai2+ variations in response to these imposed pHi variations. NH4Cl and procaine increased Cai2+ in both unactivated and activated eggs. Procaine was found to alkalinize the egg cytoplasm, whereas the other weak base, NH4Cl, acidified the egg cytoplasm. On the other hand, CO2 was found to acidify the cytoplasm and to substantially decrease Cai2+, also in unactivated and activated eggs. In addition, CO2 triggered an increase in the conductance of the plasma membrane to Cl- ions, similarly to what had been found previously with weak bases (Charbonneau, M. (1989) Cell Differ. Develop. 26, 39-52). These Cl- channels, similarly to the sperm-triggered Cl- channels during the fertilization potential, are supposed to be Ca2(+)-sensitive. Therefore, the changes in Ca2+ observed in response to CO2 do not seem to be responsible for the opening of these Cl- channels, which would rather be triggered by an increase in Cai2+ localized near the plasma membrane. We conclude therefore that weak acids and bases represent appropriate tools for studying cytosolic Ca2+ homeostasis, but not for dissecting the complex pathways involved in signal transduction.
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Dates et versions

hal-01917484 , version 1 (09-11-2018)

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  • HAL Id : hal-01917484 , version 1
  • PUBMED : 1704800

Citer

N Grandin, M. Charbonneau. Changes in intracellular free calcium activity in Xenopus eggs following imposed intracellular pH changes using weak acids and weak bases.. BBA - Biochimica et Biophysica Acta, 1991, pp.242-50. ⟨hal-01917484⟩
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