EFFECT OF CA2-FREE SEAWATER TREATMENT ON 1-METHYLADENINE PRODUCTION IN STARFISH OVARIAN FOLLICLE CELLS()

When follicle cells from ovaries of the starfish Asterina pectinifera were washed with Ca2+-free seawater (CaFSW), the production of 1-methy ladenine (1-MeAde) in response to gonad-stimulating substance (GSS) de creased to a large degree. The cyclic AMP content of CaFSW-treated fol licle cells was much lower than that of non-treated cells, and the lev el was increased slightly by GSS, but not to a degree sufficient for p roduction of 1-MeAde. The production of 1-MeAde and cyclic AMP in the presence of GSS was dependent on extracellular Ca2+ concentration, and was considerably reduced at a Ca2+ concentration below 1 mM. Thus, th e decrease of 1-MeAde production by follicle cells after treatment wit h CaFSW is due to the low levels of cAMP. Furthermore, an ADP-ribosyla tion experiment using [alpha-P-32]NAD(+) in the presence of cholera to xin and pertussis toxin with membrane preparations of follicle cells t reated with CaFSW revealed the presence of two types (stimulatory and inhibitory) of G-proteins. However, activity of the adenylyl cyclase w as not influenced by GSS regardless of the presence or absence of GTP. These findings may suggest that GSS is unable to bind to its receptor in follicle cells after washing with CaFSW.