Involvement of cAMP in initiating maturation of the brittle-star Amphipholis kochii oocytes: Induction of oocyte maturation by inhibitors of cyclic nucleotide phosphodiesterase and activators of adenylate cyclase

Abstract

The maturation of brittle-star ( Amphipholis kochii) oocytes, i.e., the reinitiation of meiosis accompanied by germinal vesicle breakdown (GVBD) and the acquisition of fertilizability, was induced by acid (pH 3.0) seawater containing 10 m M cAMP. Oocyte maturation was also induced by seawater of normal pH (pH 8.0) that contained either an inhibitor of cyclic nucleotide phosphodiesterase (25 m M theophylline, 25 m M caffeine) or an activator of adenylate cyclase (100 μ M forskolin, 0.6 μ M cholera toxin). Experiments in which the oocytes were treated with forskolin or theophylline for various periods of time demonstrated that there was a positive correlation between the oocyte cAMP level measured by radioimmunoassay and the extent of GVBD induced in each treatment: both increased as the treatment period became longer and about a threefold increase in cAMP level induced 50% GVBD. These results indicate that an increase in cAMP level initiates maturation of the brittle-star oocytes.