Figure 4.

FGF-2 increases activity of PKA in NIH 3T3 cells without detectable change in intracellular cAMP concentration. (a) FGF-2 controls the activity of PKA. Serum-starved NIH 3T3 cells were treated with indicated growth factors (10 ng/ml) and PKA-activators 8-Br-cAMP (200 μM) for 30 min. H-89 (10 μM) was added 30 min before FGF-2. Phosphorylation of the PKA-specific substrate Kemptide was measured by liquid scintillation counting. Means and standard deviations of four independent experiments are shown. (b) FGF-2 induction does not increase the intracellular concentration of cAMP. NIH 3T3 cells were deprived of serum and treated with FGF-2 (10 ng/ml) or IBMX (1 mM) with forskolin (10 μM) for indicated times. Changes in intracellular cAMP concentration were measured with cAMP-specific ELISA.