Fig. 8. Inhibition of oocyte- and GDF9-stimulated SMAD3 activation using the ALK4/5/7 kinase inhibitor, SB431542. Mural GCs were transiently transfected during culture with either a SMAD3-responsive CAGA-luciferase or a SMAD1-responsive BRE-luciferase reporter plasmid. (A) CAGA-luciferase was stimulated by TGFß1, which in turn was dose-dependently antagonised by treatment with SB431542. The carrier, DMSO, at a v/v dose equivalent to 0.5 µM of SB431542, did not affect TGFß-induced mural GC CAGA-luciferase activity. (B) BMP6 (50 ng/ml)-stimulated BRE-luciferase activity was not affected by a maximum dose of 2 µM SB431542. (C) Treatment of mural GCs with 0.5 µM SB431542 completely antagonised GDF9-activation (60 ng/ml) and oocyte-activation (60 oocytes/well) of SMAD3-responsive CAGA luciferase activity; asterisk indicates significantly different to control (oocytes alone; P<0.05).