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Protein synthesis inhibitors prevent both spontaneous and hormone-dependent maturation of isolated mouse oocytes
1Biology Department, Marquette University, Milwaukee, Wisconsin 53233.
Abstract:
The present study was carried out to examine the role of protein synthesis in mouse oocyte maturation in vitro. In the first part of this study, the effects of cycloheximide (CX) were tested on spontaneous meiotic maturation when oocytes were cultured in inhibitor-free medium. CX reversibly suppressed maturation of oocytes as long as maturation was either initially prevented by the phosphodiesterase inhibitor, 3-isobutyl-1-methyl-xanthine (IBMX), or delayed by follicle-stimulating hormone (FSH). In the second part of this study, the actions of protein synthesis inhibitors were tested on hormone-induced maturation. CEO were maintained in meiotic arrest for 21-22 h with hypoxanthine, and germinal vesicle breakdown (GVB) was induced with follicle-stimulating hormone (FSH). Three different protein synthesis inhibitors [CX, emetine (EM), and puromycin (PUR)] each prevented the stimulatory action of FSH on GVB in a dose-dependent fashion. This was accompanied by a dose-dependent suppression of 3H-leucine incorporation by oocyte-cumulus cell complexes. The action of these inhibitors on FSH- and epidermal growth factor (EGF)-induced GVB was next compared. All three drugs lowered the frequency of GVB in the FSH-treated groups, below even that of the controls (drug + hypoxanthine); the drugs maintained meiotic arrest at the control frequencies in the EGF-treated groups. Puromycin aminonucleoside, an analog of PUR with no inhibitory action on protein synthesis, had no effect. The three inhibitors also suppressed the stimulatory action of FSH on oocyte maturation when meiotic arrest was maintained with the cAMP analog, dbcAMP.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Protein synthesis is crucial for mouse oocyte maturation. Inhibitors like cycloheximide blocked hormone-induced germinal vesicle breakdown, highlighting protein synthesis
Area of Science:
- Reproductive Biology
- Molecular Endocrinology
- Cellular Physiology
Background:
- Oocyte maturation is a complex process involving precise molecular events.
- The role of protein synthesis during meiotic maturation requires further elucidation.
Purpose of the Study:
- To investigate the necessity of protein synthesis for in vitro mouse oocyte maturation.
- To determine the impact of protein synthesis inhibitors on hormone-induced meiotic resumption.
Main Methods:
- Oocytes were cultured in vitro with or without protein synthesis inhibitors (cycloheximide, emetine, puromycin).
- Meiotic arrest was maintained using hypoxanthine, IBMX, or dbcAMP.
- Germinal vesicle breakdown (GVB) induction was achieved using follicle-stimulating hormone (FSH) or epidermal growth factor (EGF).
- Protein synthesis inhibition was assessed by measuring 3H-leucine incorporation.
Main Results:
- Protein synthesis inhibitors (cycloheximide, emetine, puromycin) dose-dependently prevented FSH-induced GVB.
- These inhibitors suppressed 3H-leucine incorporation in oocyte-cumulus cell complexes.
- Inhibitors blocked FSH-induced maturation but not EGF-induced GVB, suggesting distinct pathways.
- A non-inhibitory analog of puromycin had no effect, confirming the specificity of protein synthesis inhibition.
Conclusions:
- Active protein synthesis is essential for FSH-stimulated mouse oocyte maturation.
- The findings differentiate the molecular requirements for maturation induced by FSH versus EGF.
- This study underscores the critical role of newly synthesized proteins in regulating meiotic resumption.