Cyclic adenosine 3’5’monophosphate (cAMP) regulates meiotic maturation in goldfish oocytes Carassius auratus (Teleostei: Cyprinidae)

Abstract

A good understanding of the mechanism of oocyte development and maturation, and the regulatory factors involved therein are important for the success of a breeding program especially of species used in aquaculture. It is crucial in a breeding program for females to supply high quality mature oocytes, which is generally achieved by fine-tuning oocyte meiotic arrest and resumption progression. Therefore, knowledge of the oocyte maturation process is fundamental for the development of methodologies to increase the success of fish production in aquaculture. TheFigure regulations of oocyte maturation still are not totally understood. The hypothesis whether elevated levels or a drop in intraoocyte cAMP triggers resumption of meiotic maturation was investigated in denuded goldfish oocytes. In the presence of agents that elevate cAMP like forskolin, dibutyryl cAMP, isobutyl methylxanthine, maturation of denuded oocytes was inhibited. Whereas 2’deoxyadenosine-3-monophosphate, an inhibitor of adenylate cyclase promoted oocyte maturation. Forskolin decreased spontaneous maturation as well as hormone-induced maturation of goldfish oocytes. At 10 µM forskolin added up to 4 h after hormonal stimulation completely inhibited oocyte maturation. Beyond 4 h, however, when oocyte maturation had already started, forskolin can no longer inhibit maturation. Intraoocyte cAMP assayed in denuded oocytes with or without hormonal stimulation decreased immediately within 30 minutes. With forskolin, it did not cause a significant decrease in cAMP not until at 4 h. The results were consistent with the findings that elevated levels of cAMP maintain meiotic arrest while a decrease in cAMP is necessary and sufficient to trigger resumption of meiotic maturation.