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A more recent version of this article appeared on November 1, 2002
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Submitted on April 30, 2002
Revised on June 25, 2002
Accepted on July 29, 2002
1 Hormones, Growth and Development Program, Ottawa Health Research Institute; and Cellular and Molecular Medicine, University of Ottawa
2 Hormones, Growth and Development Program, Ottawa Health Research Institute
3 Hormones, Growth and Development Program, Ottawa Health Research Institute, Departments of Obstetrics and Gynecology, (Division of Reproductive Medicine), and Cellular and Molecular Medicine, University of Ottawa; and Human IVF Laboratory, Ottawa Hospital, Ottawa, Ontario, K1Y 4E9
* Corresponding author. E-mail address: jbaltz{at}ohri.ca.
The HCO3-/Cl- exchanger is quiescent in the unfertilized mouse egg, but is highly active in regulating intracellular pH in the early embryo and required for normal development. We show here that the HCO3-/Cl- exchanger is active in first meiotic prophase (GV) oocyte, but inactivated during meiotic metaphase before the MI to MII transition. Reactivation does not occur until the activated egg enters interphase. A quiescent HCO3-/Cl- exchanger is not simply a general feature of metaphase, since activity did not decrease during first mitotic metaphase. Inactivation of the HCO3-/Cl- exchanger during MI coincided with the activation of MAP kinase (MAPK), while its reactivation coincided with the loss of MAPK activity after egg activation. Maintaining high MAPK activity after egg activation prevented the normal reactivation of the HCO3-/Cl- exchanger. Inactivating MAPK in unfertilized MII eggs resulted in HCO3-/Cl- exchanger activation. Preventing MAPK activation during first meiotic metaphase prevented the inactivation of HCO3-/Cl- exchange. Conversely, activating MAPK in the GV oocyte resulted in inactivation of HCO3-/Cl- exchange. These results imply that the HCO3-/Cl- exchanger in mouse oocytes is negatively regulated by MAPK. Thus, suppression of pH-regulatory mechanisms during meiosis is a novel function of MAPK and cytostatic factor (CSF) activity in the oocyte.
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  G. FitzHarris, V. Siyanov, and J. M. Baltz Granulosa cells regulate oocyte intracellular pH against acidosis in preantral follicles by multiple mechanisms Development, December 1, 2007; 134(23): 4283 - 4295. [Abstract] [Full Text] [PDF]
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G. FitzHarris and J. M. Baltz Granulosa cells regulate intracellular pH of the murine growing oocyte via gap junctions: development of independent homeostasis during oocyte growth Development, February 15, 2006; 133(4): 591 - 599. [Abstract] [Full Text] [PDF]
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