Effects of EDTA Saturated With Ca2+ (Ca-EDTA) on Pig, Bovine and Mouse Oocytes at the Germinal Vesicle Stage During Maturation Culture and the Involvement of Chelation of Zn2+ in Pronuclear Formation Induction by Ca-EDTA

Reproduction. 2002 Aug;124(2):235-40.

Abstract

EDTA saturated with Ca(2+), Fe(3+) or Cu(2+) can induce parthenogenetic activation of pig oocytes at the germinal vesicle stage, whereas EDTA saturated with Zn(2+), which is unable to chelate Zn(2+), does not, indicating that chelation of Zn(2+) with EDTA saturated with Ca(2+) (Ca-EDTA) in maturing pig oocytes plays a pivotal role in the induction of parthenogenetic activation of oocytes. In the present study, the involvement of Zn(2+) chelation in the induction of parthenogenetic activation of pig oocytes at the germinal vesicle stage was confirmed first by examining the effects of concomitant addition of Zn(2+), Cu(2+) or Ni(2+) at various concentrations together with 1 mmol Ca-EDTA l(-1) to the maturation medium. The titration experiments revealed that the pronuclear formation induced by 1 mmol Ca-EDTA l(-1) was completely inhibited by the addition of > 30 micromol Zn(2+) l(-1) to the medium, but not by the addition of Cu(2+) and Ni(2+) at any concentration examined. Second, bovine and mouse oocytes at the germinal vesicle stage were cultured in medium with or without 1 mmol Ca-EDTA l(-1) for 48 h to examine the effects of Ca-EDTA treatment on these oocytes during maturation culture. Most (70-86%) of the bovine oocytes that underwent germinal vesicle breakdown matured to the MII stage via the MI phase, regardless of whether Ca-EDTA was present for the first 24 h of culture. However, 61% of oocytes that had been cultured with Ca-EDTA for 48 h formed a pronucleus without a second polar body, whereas oocytes cultured in the absence of Ca-EDTA were not observed to form a pronucleus at any time during culture. However, even when mouse oocytes at the germinal vesicle stage were cultured for up to 48 h in maturation medium containing Ca-EDTA, pronuclear formation was not observed. Finally, when bovine oocytes that had been cultured with 1 mmol Ca-EDTA l(-1) for 48 h from the germinal vesicle stage were cultured further in medium without Ca-EDTA that was supplemented with 5% fetal calf serum, only 26% of the oocytes developed to the cleaved stage, and none could develop further.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / antagonists & inhibitors
  • Calcium / pharmacology*
  • Cattle
  • Chelating Agents / pharmacology*
  • Copper / pharmacology
  • Edetic Acid / antagonists & inhibitors
  • Edetic Acid / pharmacology*
  • Female
  • In Vitro Techniques
  • Mice
  • Nickel / pharmacology
  • Oocytes / drug effects*
  • Oocytes / growth & development
  • Parthenogenesis / drug effects
  • Swine
  • Zinc / pharmacology*

Substances

  • Chelating Agents
  • Copper
  • Nickel
  • Edetic Acid
  • Zinc
  • Calcium