QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 11 January 2006
doi: 10.1242/dev.02246

This Article Figures Only Full Text Full Text (PDF) All Versions of this Article: dev.02246v1 133/4/591    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by FitzHarris, G. Articles by Baltz, J. M. Search for Related Content PubMed PubMed Citation Articles by FitzHarris, G. Articles by Baltz, J. M.

Granulosa cells regulate intracellular pH of the murine growing oocyte via gap junctions: development of independent homeostasis during oocyte growth

¹ Hormones, Growth and Development Program, Ottawa Health Research Institute, Ottawa, ON K1Y 4E9, Canada.
² Department of Obstetrics and Gynecology (Division of Reproductive Medicine), University of Ottawa, Ottawa, ON K1Y 4E9, Canada.
³ Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1Y 4E9, Canada.

^* Author for correspondence (e-mail: jbaltz{at}ohri.ca)

Accepted 13 December 2005

Oocytes grow within ovarian follicles in which the oocyte is coupled to the surrounding granulosa cells by gap junctions. It was previously found that small growing oocytes isolated from juvenile mice and freed of their surrounding granulosa cells (denuded) lacked the ability to regulate their intracellular pH (pH_i), did not exhibit the pH_i-regulatory HCO₃^-/Cl^- and Na⁺/H⁺ exchange activities found in fully-grown oocytes, and had low pH_i. However, both exchangers became active as oocytes grew near to full size, and, simultaneously, oocyte pH_i increased by approximately 0.25 pH units. Here, we show that, in the more physiological setting of the intact follicle, oocyte pH_i is instead maintained at 7.2 throughout oocyte development, and the growing oocyte exhibits HCO₃^-/Cl^- exchange, which it lacks when denuded. This activity in the oocyte requires functional gap junctions, as gap junction inhibitors eliminated HCO₃^-/Cl^- exchange activity from follicle-enclosed growing oocytes and substantially impeded the recovery of the oocyte from an induced alkalosis, implying that oocyte pH_i may be regulated by pH-regulatory exchangers in granulosa cells via gap junctions. This would require robust HCO₃^-/Cl^- exchange activity in the granulosa cells, which was confirmed using oocytectomized (OOX) cumulus-oocyte complexes. Moreover, in cumulus-oocyte complexes with granulosa cells coupled to fully-grown oocytes, HCO₃^-/Cl^- exchange activity was identical in both compartments and faster than in denuded oocytes. Taken together, these results indicate that growing oocyte pH_i is controlled by pH-regulatory mechanisms residing in the granulosa cells until the oocyte reaches a developmental stage where it becomes capable of carrying out its own homeostasis.

Key words: pH-regulation, Oocyte, Granulosa cells, Gap junctions

This article has been cited by other articles:

				T. Y. Li, D. Colley, K. J. Barr, S.-P. Yee, and G. M. Kidder Rescue of oogenesis in Cx37-null mutant mice by oocyte-specific replacement with Cx43 J. Cell Sci., December 1, 2007; 120(23): 4117 - 4125. [Abstract] [Full Text] [PDF]

				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]