Figure 4
Intracellular cAMP production was enhanced by ISO but reversed by β-AR antagonists. A, cAMP levels after 5 min stimulation with the indicated concentrations of ISO. Curve was drawn according to simple Michaelis-Menten kinetics, yielding an EC50 of 180 ± 37 nM. B, HemECs were pre-treated with 10 μM MET or 10 μM ICI for 1 h followed by stimulation with 1 μM ISO for 5 min. Positive controls consisted of cells treated with only 100 μM forskolon for 5 min. All reactions took place in the presence of 100 μM IBMX. cAMP levels were measured using the enzyme immunoassay method. The results are shown as the mean ± SD of triplicate assays from one of three identical experiments. * P<0.05 when compared with the ISO-untreated control, † P<0.05 when compared with the ISO-treated control.