Inhibition of maturation by PCP. (A) PCP was added to indicate concentrations, and then maturation was induced by 0.1 μM of 17,20β-DHP (a), 1 μM of DES (b) or 10 μM of TAM (c). (B) Oocytes were treated with 1 μM of PCP for the periods indicated, and then PCP was washed-out by changing the medium three times. Then, maturation was induced by adding 0.1 μM of 17,20β-DHP or ethanol (EtOH). Incubation with the mixture of PCP and 17,20β-DHP is indicated as cont. (C) Oocytes were treated with combinations of indicated concentrations of PCP and 17,20β-DHP. %GVBD was calculated by determining the percentage of oocytes that had undergone germinal vesicle breakdown (GVBD) among more than 20 oocytes cultured for three hours in each experiment. Each value is the mean of three separate experiments using ovaries of three different females. Vertical lines indicate standard deviation.