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Regular Article |
a Research Laboratories of Schering AG, Berlin, Germany
b Health Care Discovery of Novo Nordisk A/S, Copenhagen, Denmark
c Department of Obstetrics and Gynaecology, Göteborg University, Sahlgrenska University Hospital, Göteborg, S-41345, Sweden
ABSTRACT
Meiosis-activating sterols (MAS) have been found to induce meiotic maturation in mouse oocytes in vitro. In the present study we have extended these observations by investigating the effects of follicular fluid MAS (FF-MAS) on rat oocyte maturation in vitro and ex vivo. Rat oocytes freed from their follicles were cultured with FF-MAS (0 µM, 1 µM, 3 µM, 10 µM, 30 µM) for 22 h in a medium containing the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX; 250 µM). A dose-dependent significant increase in germinal vesicle breakdown (GVB) was observed after adding FF-MAS to the culture medium in both cumulus-enclosed (CEO) and denuded (DO) oocytes. A time course study (0, 3, 8, 14, and 22 h) showed a significant increase in GVB after 14 h when DO and CEO were cultured in the presence of 10 µM FF-MAS + 250 µM IBMX. Furthermore immature rats were primed with eCG (20 IU) and 48 h later perfused ex vivo for 12 h in a recirculating system with either FF-MAS (0 µM, 10 µM, 30 µM, 60 µM), cholesterol (60 µM), or LH (0.2 µg/ml) in the presence of 200 µM IBMX, respectively. In addition, ovarian perfusion was carried out with FF-MAS (30 µM, 60 µM) or 0.2 µg/ml LH in the absence of IBMX. After 12 h, oocytes were freed from the ovaries and checked for GVB. By using the ex vivo perfused rat ovary, we found that FF-MAS, starting at 30 µM, was dose-dependently able to overcome IBMX-induced meiotic arrest leading to a comparable increase in GVB as was observed for LH. Furthermore, it was found that FF-MAS in the absence of IBMX was also able to induce meiotic maturation. Our data are consistent with the notion that the maturation-inducing effects of FF-MAS are mediated by different mechanisms compared to spontaneous maturation.
First decision: 21 January 2000.
1 Correspondence: Christa Hegele-Hartung, FC/HT Research of Schering AG, Müllerstrasse 170-178, D-13342 Berlin, Germany. FAX: 49 30 46818056;christa.hegelehartung{at}schering.de
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