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This Article Full Text Full Text (PDF) All Versions of this Article: 78/2/307    most recent biolreprod.107.064527v1 Alert me when this article is cited Alert me if a correction is posted Citation Map 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 Google Scholar Google Scholar Articles by Martín-Romero, F. J. Articles by Álvarez, I. S Search for Related Content PubMed PubMed Citation Articles by Martín-Romero, F. J. Articles by Álvarez, I. S Agricola Articles by Martín-Romero, F. J. Articles by Álvarez, I. S

Store-Operated Calcium Entry in Human Oocytes and Sensitivity to Oxidative Stress¹

Departamento de Bioquímicay Biología Molecular,³ Departamento de Biología Celular,⁴ and Departamento de Terapéutica Medico-Quirúrgica,⁵Reproduction and Development Group (REDES), Universidad de Extremadura, Badajoz-06071, Spain Instituto Extremeño de Reproducción Asistida (IERA),⁶ Badajoz-06004, Spain

ABSTRACT

Calcium signaling is a cellular event that plays a key role at many steps of fertilization and early development. However, little is known regarding the contribution of extracellular Ca²⁺ influx into the cell to this signaling in gametes and early embryos. To better know the significance of calcium entry on oocyte physiology, we have evaluated the mechanism of store-operated calcium entry (SOCE) in human metaphase II (MII) oocytes and its sensitivity to oxidative stress, one of the major factors implicated in the outcome of in vitro fertilization (IVF) techniques. We show that depletion of intracellular Ca²⁺ stores through inhibition of sarco(endo)plasmic Ca²⁺-ATPase with thapsigargin triggers Ca²⁺ entry in resting human oocytes. Ba²⁺ and Mn²⁺ influx was also stimulated following inhibition, and Ca²⁺ entry was sensitive to pharmacological inhibition because the SOCE blocker 2-aminoethoxydiphenylborate (2-APB) reduced calcium and barium entry. These results support the conclusion that there is a plasma membrane mechanism responsible for the capacitative divalent cation entry in human oocytes. Moreover, the Ca²⁺ entry mechanism described in MII oocytes was found to be highly sensitive to oxidative stress. Hydrogen peroxide, at micromolar concentrations that could mimic culture conditions in IVF, elicited an increase of [Ca²⁺]_i that was dependent on the presence of extracellular Ca²⁺. This rise was preventable by 2-APB, indicating that it was mainly due to the enhanced influx through store-operated calcium channels. In sum, our results demonstrate the occurrence of SOCE in human MII oocytes and the modification of this pathway due to oxidative stress, with possible consequences in IVF.

2-APB, calcium, calcium channels, hydrogen peroxide, oocyte, oxidative stress, store-operated calcium entry, thapsigargin

¹Supported by grants BFU2004-04500 from the Spanish Ministerio de Educación y Ciencia, SCSS-0510 and SCSS-0676 from the Consejeria de Sanidad y Consumo (Junta de Extremadura), and PRIB06B300 from the Consejeria de Infraestructuras y Desarrollo Tecnológico (Junta de Extremadura).

Correspondence: ²Francisco Javier Martín-Romero, Department of Biochemistry and Molecular Biology, Science Faculty, University of Extremadura, Avenida de Elvas s/n, 06071-Badajoz, Spain. FAX: 34 924 289 419; e-mail: fjmartin{at}unex.es