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Resumption of rat oocyte meiosis is paralleled by a decrease in guanosine 3',5'-cyclic monophosphate (cGMP) and is
J Törnell1, H Billig, T Hillensjö
1Department of Physiology, University of Göteborg, Sweden.
Abstract:
The aim of the present study was to measure the level of cyclic GMP (cGMP) compared with the level of cyclic AMP (cAMP) in rat oocytes during resumption of meiosis I (oocyte maturation) and to microinject these cyclic nucleotides into the oocyte to study their effects on oocyte maturation. Immature oocytes were obtained from prepubertal rats primed with pregnant mare's serum gonadotropin. OOcytes were isolated adn short-term cultured under conditions enabling spontaneous maturation. The levels of cGMP and cAMP decreased in the oocyte during spontaneous maturation (from 0.41 to 0.25 and from 0.64 to 0.42 fmol per oocyte respectively). The decrease was observed during the first hour of culture, and no further decline was seen after 2 h. Microinjection of cGMP or cAMP into isolated immature oocytes delayed the spontaneous maturation, cGMP being slightly more effective than cAMP, whereas 2-deoxy-cAMP (which does not stimulate protein kinase A) did not. These results demonstrate for the first time that the level of cGMP decreases in the oocyte parallel to spontaneous meiosis, as already shown for cAMP. This suggests that cGMP, as well as cAMP, may be of importance for regulating this process. This assumption is further supported by data demonstrating a delay in the maturation of oocytes injected with cGMP.
Insights
Cyclic GMP (cGMP) and cyclic AMP (cAMP) levels decrease during rat oocyte maturation. Microinjecting these cyclic nucleotides delays maturation, suggesting their crucial role in regulating this process.
Area of Science:
- Reproductive Biology
- Cell Signaling
- Molecular Endocrinology
Background:
- Oocyte maturation is a critical process in female reproduction.
- Cyclic AMP (cAMP) is known to regulate oocyte maturation.
- The role of cyclic GMP (cGMP) in oocyte maturation requires further investigation.
Purpose of the Study:
- To quantify cyclic GMP (cGMP) and cyclic AMP (cAMP) levels in rat oocytes during meiosis I resumption.
- To investigate the effects of microinjecting cGMP and cAMP on oocyte maturation.
Main Methods:
- Immature rat oocytes were cultured to allow spontaneous maturation.
- Levels of cGMP and cAMP were measured during oocyte maturation.
- cGMP and cAMP were microinjected into immature oocytes to assess their impact on maturation.
Main Results:
- Both cGMP and cAMP levels significantly decreased in oocytes during spontaneous maturation within the first hour of culture.
- Microinjection of cGMP or cAMP into immature oocytes delayed spontaneous maturation.
- cGMP demonstrated a slightly greater inhibitory effect on maturation compared to cAMP.
- 2-deoxy-cAMP, a non-activator of protein kinase A, did not affect maturation.
Conclusions:
- This study provides the first evidence that cGMP levels decrease in parallel with spontaneous meiosis in oocytes, similar to cAMP.
- Both cGMP and cAMP appear to play important regulatory roles in oocyte maturation.
- The findings support the hypothesis that cGMP is involved in regulating oocyte maturation.