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Transmembrane regulation of intracellular calcium by a plasma membrane sodium/calcium exchanger in mouse ova

Transmembrane regulation of intracellular calcium by a plasma membrane sodium/calcium exchanger in mouse ova
Transmembrane regulation of intracellular calcium by a plasma membrane sodium/calcium exchanger in mouse ova
Regulation of cytoplasmic free calcium concentration ([Ca2+)]i) is a key factor for maintenance of viability of cells, including oocytes. Indeed, during fertilization of an ovum, [Ca2+]i is known to undergo oscillations, but it is unknown how basal [Ca2+]i or calcium oscillations are regulated. In the present study we investigated the role of the plasma membrane in regulating [Ca2+]i of metaphase II-arrested mouse oocytes (ova). Ova were collected from B6C3F1 mice treated with eCG (10 IU) and hCG (5 IU), and intracellular calcium was determined by means of fura-2. Extracellular calcium flux across the zona pellucida was detected noninvasively by a calcium ion-selective, self-referencing microelectrode that was positioned by a computer-controlled micromanipulator. Under basal conditions ova exhibited a calcium net efflux of 20.6 +/- 5.2 fmol/cm2 per sec (n = 69). Treatment of ova with ethanol (7%) or thapsigargin (25 nM-2.5 microM) transiently increased intracellular calcium and stimulated calcium efflux that paralleled levels of [Ca2+]i. The presence of a Na+/Ca2+ exchanger was indicated by experiments employing both bepridil, an inhibitor of Na+/Ca2+ exchange, and sodium-depleted media. In the presence of bepridil, a net influx of calcium was revealed across the zona pellucida, which was reflected by an increase in the [Ca2+]i. In addition, replenishment of extracellular sodium to ova that had been incubated in sodium-depleted media induced a large calcium efflux, consistent with the actions of Na+/Ca2+ exchange. Sodium/calcium exchange in mouse ova may be an important mechanism that regulates [Ca2+]i.
1137-1143
Pepperell, J.R.
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Kommineni, K.
8cbd7e98-76b4-460f-af46-ba72796cecd6
Buradagunta, S.
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Smith, P.J.
003de469-9420-4f12-8f0e-8e8d76d28d6c
Keefe, D.L.
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Pepperell, J.R.
c0212c6c-d5e9-4050-a0d0-318870f86f8e
Kommineni, K.
8cbd7e98-76b4-460f-af46-ba72796cecd6
Buradagunta, S.
8c9f3d01-29e5-42bf-b876-403fb50680e9
Smith, P.J.
003de469-9420-4f12-8f0e-8e8d76d28d6c
Keefe, D.L.
5a3dd68e-4834-477e-ac32-ce637755965c

Pepperell, J.R., Kommineni, K., Buradagunta, S., Smith, P.J. and Keefe, D.L. (1999) Transmembrane regulation of intracellular calcium by a plasma membrane sodium/calcium exchanger in mouse ova. Biology of Reproduction, 60 (5), 1137-1143. (doi:10.1095/?biolreprod60.5.1137). (PMID:10208975)

Record type: Article

Abstract

Regulation of cytoplasmic free calcium concentration ([Ca2+)]i) is a key factor for maintenance of viability of cells, including oocytes. Indeed, during fertilization of an ovum, [Ca2+]i is known to undergo oscillations, but it is unknown how basal [Ca2+]i or calcium oscillations are regulated. In the present study we investigated the role of the plasma membrane in regulating [Ca2+]i of metaphase II-arrested mouse oocytes (ova). Ova were collected from B6C3F1 mice treated with eCG (10 IU) and hCG (5 IU), and intracellular calcium was determined by means of fura-2. Extracellular calcium flux across the zona pellucida was detected noninvasively by a calcium ion-selective, self-referencing microelectrode that was positioned by a computer-controlled micromanipulator. Under basal conditions ova exhibited a calcium net efflux of 20.6 +/- 5.2 fmol/cm2 per sec (n = 69). Treatment of ova with ethanol (7%) or thapsigargin (25 nM-2.5 microM) transiently increased intracellular calcium and stimulated calcium efflux that paralleled levels of [Ca2+]i. The presence of a Na+/Ca2+ exchanger was indicated by experiments employing both bepridil, an inhibitor of Na+/Ca2+ exchange, and sodium-depleted media. In the presence of bepridil, a net influx of calcium was revealed across the zona pellucida, which was reflected by an increase in the [Ca2+]i. In addition, replenishment of extracellular sodium to ova that had been incubated in sodium-depleted media induced a large calcium efflux, consistent with the actions of Na+/Ca2+ exchange. Sodium/calcium exchange in mouse ova may be an important mechanism that regulates [Ca2+]i.

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Published date: May 1999

Identifiers

Local EPrints ID: 190245
URI: http://eprints.soton.ac.uk/id/eprint/190245
PURE UUID: 3bd639e1-1db2-43bb-aac2-96c1018db6b9
ORCID for P.J. Smith: ORCID iD orcid.org/0000-0003-4400-6853

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Date deposited: 17 Jun 2011 09:28
Last modified: 21 Nov 2021 03:04

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Contributors

Author: J.R. Pepperell
Author: K. Kommineni
Author: S. Buradagunta
Author: P.J. Smith ORCID iD
Author: D.L. Keefe

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