4-AP does not affect granulosa cell viability in serum-supplemented cultures. A) The numbers of viable cells (mean ± SEM) 24 h after treatment for GC cultures maintained in the absence (CON) of FSH with and without the addition of 2 mM 4-AP (10 culture wells from 5 different GC isolations), and in the presence of FSH with and without the addition of 2 mM 4-AP (8 culture wells from 4 GC isolations). B) Western blot analysis of proliferating cell nuclear antigen (PCNA, left) and actin (loading control, right) in GC lysates (40 μg protein/lane) from cultures described in panel A. Arrows indicate molecular mass (kDa). The results shown are representative of 3 independent experiments.