Induction and inhibition of oocyte maturation by EDCs in zebrafish
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Induction and inhibition of oocyte maturation by EDCs in zebrafish Toshinobu Tokumoto*1,2, Mika Tokumoto1,2 and Yoshitaka Nagahama2,3 Address: 1Department of Biology and Geosciences, Faculty of Science, National University Corporation Shizuoka University, Shizuoka 422-8529, Japan, 2CREST Research Project, Japan Science and Technology Corporation, Kawaguchi 332-0012, Japan and 3Laboratory of Reproductive Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan Email: Toshinobu Tokumoto* - [email protected]; Mika Tokumoto - [email protected]; Yoshitaka Nagahama - [email protected] * Corresponding author
Published: 09 December 2005 Reproductive Biology and Endocrinology 2005, 3:69
doi:10.1186/1477-7827-3-69
Received: 05 November 2005 Accepted: 09 December 2005
This article is available from: http://www.rbej.com/content/3/1/69 © 2005 Tokumoto et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: Oocyte maturation in lower vertebrates is triggered by maturation-inducing hormone (MIH), which acts on unidentified receptors on the oocyte surface and induces the activation of maturation-promoting factor (MPF) in the oocyte cytoplasm. We previously described the induction of oocyte maturation in fish by an endocrine-disrupting chemical (EDC), diethylstilbestrol (DES), a nonsteroidal estrogen. Methods: In this study, stimulatory and inhibitory effects of EDCs and natural steroids on oocyte maturation were examined in zebrafish. For effective agents, some details about the mechanism in induction or inhibition of maturation were examined. Possible groups of DES interacting with the MIH receptor are discussed based on relative potency of steroids to induce maturation. Results: Among agents tested, tamoxifen (TAM) and its metabolite 4-hydroxytamoxifen (4-OHT) showed stimulatory activity similar to DES. The time courses of the change in germinal vesicle breakdown and an intracellular molecular event (the synthesis of cyclin B) induced by TAM were indistinguishable from those induced by MIH. In contrast, pentachlorophenol (PCP) had a potent inhibitory effect on MIH-induced oocyte maturation. PCP inhibited not only MIH-induced maturation but also DES- and TAM-induced maturation. Methoxychlor also inhibited maturation when oocytes were pre-treated with this agent. Conclusion: These results suggest that EDCs act as agonists or antagonists in the induction of oocyte maturation in fish.
Background Fish oocytes provide an appropriate experimental system with which to investigate the molecular mechanisms controlling meiosis and the embryonic cell cycle. Several factors responsible for the regulation of meiotic maturation in fish oocytes have been identified. These include the isolation and characteriza
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