4-AP decreases cAMP and StAR in PGC-2 cultures. A) Accumulation of cAMP in PGC-2 (n = 4 culture wells). PGC-2 were cultured in serum-free media (McCoy's modified 5A) in the presence of IBMX (10 μM) without (Control) or with the addition of 4-AP (2 mM) and forskolin (5 μM) for 2 h, then pelleted and lysed in HCl (0.1 N) prior to analysis of cAMP levels. B) Western blot analysis of StAR in mitochondrial extracts from PGC-2 cells (10 ug protein/lane) cultured in serum-free media for 2 h in the absence (Con) or presence of 4-AP. The results shown are representative of 3 independent experiments. Astericks indicates P < 0.05 compared with PGC-2 cultures under similar conditions in the absence of 4-AP.