Effect of methanol and Me<inf>2</inf>SO exposure on mitochondrial activity and distribution in stage III ovarian follicles of zebrafish (Danio rerio)

Authors: Zampolla, T., Spikings, E., Zhang, T. and Rawson, D.M.

Journal: Cryobiology

Volume: 59

Issue: 2

Pages: 188-194

eISSN: 1090-2392

ISSN: 0011-2240

DOI: 10.1016/j.cryobiol.2009.07.002

Abstract:

In this study the effect of cryoprotectants that have been shown to be the least toxic to zebrafish ovarian follicles (methanol and Me2SO), on mitochondria of stage III ovarian follicles was evaluated. The mitochondrial distributional arrangement, mitochondrial membrane potential, mtDNA copy number, ATP levels and ADP/ATP ratios were assessed following exposure to cryoprotectants for 30 min at room temperature. Results obtained by confocal microscopy showed that 30 min exposure to 2 M methanol induced a loss of membrane potential, although viability tests showed no decrease in survival even after 5 h post-exposure incubation. Higher concentrations of methanol (3 and 4 M) induced not only a decrease in mitochondrial membrane potential but also the loss of mitochondrial distributional arrangement, which suggested a compromised mitochondrial function. Furthermore 3 and 4 M treatments resulted in a decrease in viability assessed by Fluorescein diacetate-Propidium iodide (FDA-PI) and in a decrease in mtDNA copy number and ADP/ATP ratio after 5 h incubation following methanol exposure, indicating a delayed effect. The use of Me2SO, which is considered to be a more toxic CPA to zebrafish ovarian follicles than methanol, caused a decrease in viability and a sustained decrease in ATP levels accompanied by failure to maintain mtDNA copy number within 1 h post-exposure incubation. These results indicated that even CPAs that are considered to have no toxicity as determined by Trypan blue (TB) and FDA-PI tests can have a deleterious effect on mitochondrial activity, potentially compromising oocyte growth and embryo development. © 2009 Elsevier Inc. All rights reserved.

Source: Scopus