1-METHYLADENINE PRODUCTION BY OVARIAN FOLLICLE CELLS RESPONSIBLE FOR SPAWNING IN THE STARFISH ASTERINA-PECTINIFERA

Resumption of meiosis in starfish oocytes is induced by 1-methyladenine (1-MeAde) produced by ovarian follicle cells under the influence of gonad-stimulating substance (GSS). It has also been reported that 1-MeAde induces follicular envelope breakdown (FEBD), releasing oocytes from the ovaries; i.e., spawning. This study was undertaken to determine whether the amount of 1-MeAde produced by follicle cells is enough to induce germinal vesicle breakdown (GVBD) and FEBD in the starfish Asterina pectinifera. After incubation of an ovary with GSS at concentrations of more than 0.05 mg/ml for about 20 min, spawning started. Almost the same period of time was required for spawning after treatment with 0.1 muM 1-MeAde. However, continuous treatment with GSS was not necessary, and about 5 min of GSS application was sufficient for induction of spawning. Each oocyte is surrounded by a follicular envelope consisting of about 50 cells. 1-MeAde production by isolated follicle cells started immediately upon GSS stimulation, and the amount of I-MeAde produced in vitro was correlated with the number of follicle cells present. Thus, 50 follicle cells were shown to produce about 1.1 fmol 1-MeAde during 5 min of GSS treatment. These results confirm that the amount of 1-MeAde produced by follicle cells is sufficient for meiosis initiation and release of oocytes in starfish.