Concanavalin A induces germinal vesicle breakdown in Barnea candida (Mollusca, Pelecypoda) oocytes

Treatment of Barnea candida oocytes with 5 micrograms/ml Con A or above elicits germinal vesicle breakdown (GVBD), the timing for this event being dose dependent. At 100 micrograms/ml, GVBD occurs within 20 to 30 min, a lag time corresponding to that observed after fertilization. Con A-induced GVBD requires the presence of 2 mM external calcium during all the treatment period while at 10 mM external Ca2+, the calcium-dependent period is slightly reduced. It is sensitive to low pH Na-acetate sea water, 50 microM trifluoperazine, 20 microM D-600 or 2,4-dinitrophenol, as well as to 10 micrograms/ml cytochalasin B. A straightforward interpretation of these data would be that Con A-induced maturation is sustained by an energy-requiring effector mechanism involving intracellular contractile proteins.