Fig. 4. Specificity of oocyte-secreted factors for BMPR-II within the superfamily of TGFß type-II receptors. Mural GC thymidine incorporation was stimulated with either (A) human TGFß1 (0.5 ng/ml), (B) mouse GDF9 (40 ng/ml), (C) human activin A (10 ng/ml) or (D) 12 oocytes/well. Each mitogen was also treated separately with four different soluble receptor ectodomains; BMPR-II, TGFßR-II, ActR-IIA and ActR-IIB, each at 2 µg/ml. Bars are means ± s.e.m from triplicate wells, expressed as a fraction of the positive control (mitogen with no ECD), and are representative of four replicate experiments. An asterisk represents significant antagonism relative to the positive control (P<0.05).