Fig. 2. Dose dependence of the adenosine effect on AMPK phosphorylation and activity. (A) Phosphorylated AMPK (P-AMPK) protein levels were monitored by western blot at the indicated times after the addition of 10 µM adenosine. (B) The dose dependence of the adenosine effect was assessed after treatment for 10 minutes at the adenosine concentrations shown. Representative western blots are shown. The magnitude of the induction triggered in four independent experiments was quantified densitometrically. Results (mean ± s.e.m.) are shown as arbitrary units normalized to control values (non-treated cells). (C) Endogenous 1AMPK activity was measured 10 minutes after the addition of adenosine at the indicated concentrations. Non-linear fitting of the data was used for the estimation of the K_0.5 value. Results are the mean and s.e. from four independent experiments. The statistical significance of the adenosine effect was assessed by analysis of variance (P<0.05) combined with the Student's t-test: *P<0.05; **P<0.01; ***P<0.001. Ado, adenosine; Ctrl, control.