Mediation of cyclic adenosine 3′,5′-monophosphate in 1-methyladenine production by starfish ovarian follicle cells

Abstract

Resumption of meiosis in starfish oocytes is induced by 1-methyladenine (1-MeAde) produced by ovarian follicle cells under the influence of a gonad-stimulating substance (GSS). It has also been reproted that concanavalin A (Con A) and two serine proteolytic enzymes (trypsin and Pronase) can stimulate 1-MeAde production. This study was under-taken to determine if 1-MeAde production induced by these compounds is mediated through elevation of cAMP in starfish ( Asterina pectinifera) follicle cells. GSS at a concentration of 0.1 mg/ml significantly stimulated 1-MeAde accumulation in extracellular medium after 1–2 hr of follicle cell incubations. GSS also caused a four- to fivefold increase in intracellular levels of cAMP. The continuous presence of GSS was required for the maintenance of elevated levels of cAMP and 1-MeAde. Basal levels of intracellular cGMP were only about 20% of those of cAMP and were not influenced by treatment with GSS. At 1 m M, 3-isobutyl-1-methylxanthine (IBMX), a potent phosphodiesterase inhibitor, stimulated both 1-MeAde and cAMP production in a concentration-dependent manner. Con A and two serine proteases also raised both cAMP and 1-MeAde production. Con A-induced (1.0 mg/ml) increases in cAMP and 1-MeAde were greater than the response to GSS (0.1 mg/ml) and were completely suppressed by treatment with α-methyl- d-mannoside (10 m M), a competitive inhibitor of Con A. These results strongly suggest that cAMP is a second messenger in the production of 1-MeAde by starfish ovarian follicle cells.