The effects of quercetin on meiosis initiation in clam and starfish oocytes.

We have treated Spisula and Asterias oocytes with quercetin to determine the effects of this drug on germinal vesicle breakdown (GVBD). Quercetin (100-200 microM) reversibly inhibited GVBD when induced by excess KCl or ionophore A23187. Kinetic studies showed that quercetin blocked an early event in GVBD. Lower concentrations of quercetin (10-20 microM) blocked fertilization. However, quercetin sensitized the oocytes to initiation of GVBD by excess ions which do not normally trigger GVBD. Quercetin (100-200 microM) also blocked 1-methyladenine-induced GVBD in the starfish. In subthreshold concentrations of the hormone or in its absence, lower concentrations (20-40 microM) stimulated GVBD. The results support the hypothesis that quercetin exerts its effects on meiosis initiation through its effects on calcium sequestration.