Effect of nonselective and β1- and β2-selective agonists on cAMP accumulation in newborn rat cardiomyocytes treated or untreated with 100 μM noradrenaline Values are means ± S.E. of three to four experiments performed in duplicate. The potencies of the agonists were evaluated by their EC50 or concentration of agonist inducing 50% of the maximal cAMP accumulation expressed in -log10 EC50. Emax is the maximal response expressed in percentage over basal response. Cardiomyocytes were treated with 100 μM noradrenaline for 24 h.
β-Adrenergic Agonist | EC50 | Emax | ||||
|---|---|---|---|---|---|---|
| Untreated | Treated | Untreated | Treated | |||
| –log10 EC50 | % over basal response | |||||
| Nonselective agonist | ||||||
| Noradrenaline | 6.91 ± 0.11 | 6.54 ± 0.09 | 317 ± 37 | 123 ± 22* | ||
| Isoprenaline | 7.63 ± 0.10 | 7.51 ± 0.43 | 226 ± 24 | 51 ± 16*** | ||
| β1-Selective agonist | ||||||
| Dobutamine | 6.27 ± 0.12 | 6.13 ± 0.19 | 292 ± 60 | 56 ± 7** | ||
| β2-Selective agonist | ||||||
| Procaterol | 7.45 ± 0.10 | NR | 125 ± 12 | NR | ||
| Procaterol + PTX | 7.18 ± 0.37 | NR | 134 ± 19 | NR | ||