Stimulation of cyclic AMP-dependent protein kinase in rat atria by (–;)-CGP 12177 through an atypical β-adrenoceptor

Abstract

Mammalian hearts possess an atypical β-adrenoceptor (non-β₁, non-β₂, non-β₃) through which (–)-4-(3-t-butylamino-2-hydroxypropoxy)benzimidazol-2-one ((–)-CGP 12177) causes cardiostimulant effects. Here we showed that (–)-CGP 12177 increased the activity of adenosine 3′ : 5′-cyclic monophosphate (cyclic AMP)-dependent protein kinase in the presence of 200 nM (–)-propranolol in rat atria at a concentration (10 μM) that elicits maximum positive chronotropic and inotropic effects. The phosphodiesterase inhibitor 3-isobutyl-l-methylxanthine (IBMX) potentiated the positive chronotropic and inotropic effects of (–)-CGP 12177. We suggest that the atypical β-adrenoceptor is coupled positively to the Gs protein-adenylyl cyclase system.

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