Fig. 4. (A,B) In vitro effects of different concentrations of okadaic acid (OA) on the percentage of 2-OHE₂-induced germinal vesicle breakdown (GVBD) in Heteropneustes fossilis. (A) Effect of OA alone or co-incubated with 2-hydroxyestradiol-17ß (2-OHE₂, 5 µmol l^–1) for 24 h. (B) The effects of OA on IBMX inhibition of 2-OHE₂-induced GVBD. Values are mean ± s.e.m. Data were analyzed by one-way ANOVA (P<0.001) and Newman–Keuls' test (P<0.05). Asterisks indicate significant difference from the vehicle control (VC) group. Letters indicate comparisons with the 2-OHE₂ (A) or OA (B) group. Numbers show comparisons with 2-OHE₂ (B) group. Groups marked with the same letter or number are not significantly different and those with different letters or numbers are significantly different. NS, not significant from the vehicle control (VC) group.