Adenylyl cyclases in oocyte maturation: a characterization of AC isoforms in bovine cumulus cells.

Mammalian oocytes are arrested at the G(2)/M transition in the meiotic cell cycle. It is well known that a decrease in intraoocyte cAMP concentrations accompanies resumption of meiosis, but the precise trigger of this decrease remains a mystery. Follicular somatic cells are intimately coupled to the oocyte and are thought to transmit maturation signals to the oocyte in response to hormonal stimulation. Here, we investigate the nature of the follicular somatic cell response to hormonal stimulation by identifying and characterizing the adenylate cyclase isoforms present in bovine cumulus cells. RT-PCR and Western blot analysis revealed the presence of multiple adenylyl cyclase isoforms in bovine granulosa and cumulus cells. Pharmacological manipulation of the AC isoforms showed that multiple isoforms were indeed active. Our data indicate that the PKC inhibited adenylate cyclases IV and VI and the calcium-stimulated isoform I predominate in bovine cumulus cells.