A specific pattern of phosphodiesterases controls the cAMP signals generated by different Gs-coupled receptors in adult rat ventricular myocytes

Compartmentation of cAMP is thought to generate the specificity of G(s)-coupled receptor action in cardiac myocytes, with phosphodiesterases (PDEs) playing a major role in this process by preventing cAMP diffusion. We tested this hypothesis in adult rat ventricular myocytes by characterizing PDEs involved in the regulation of cAMP signals and L-type Ca2+ current (I-Ca,I-L) on stimulation with beta(1)-adrenergic receptors (beta(1)-ARs), beta(2)-ARs, glucagon receptors (Glu-Rs) and prostaglandin E-1 receptors (PGE(1)-Rs). All receptors but PGE(1)-R increased total cAMP, and inhibition of PDEs with 3-isobutyl-1-methylxanthine strongly potentiated these responses. When monitored in single cells by high-affinity cyclic nucleotide-gated (CNG) channels, stimulation of beta(1)-AR and Glu-R increased cAMP, whereas beta(2)-AR and PGE(1)-R had no detectable effect. Selective inhibition of PDE3 by cilostamide and PDE4 by Ro 20-1724 potentiated beta(1)-AR cAMP signals, whereas Glu-R cAMP was augmented only by PD4 inhibition. PGE(1)-R and beta(2)-AR generated substantial cAMP increases only when PDE3 and PDE4 were blocked. For all receptors except PGE(1)-R, the measurements of ICa, L closely matched the ones obtained with CNG channels. Indeed, PDE3 and PDE4 controlled beta(1)-AR and beta(2)-AR regulation of I-Ca,I-L, whereas only PDE4 controlled Glu-R regulation of I-Ca,I-L thus demonstrating that receptor-PDE coupling has functional implications downstream of cAMP. PGE(1) had no effect on I-Ca,I-L even after blockade of PDE3 or PDE4, suggesting that other mechanisms prevent cAMP produced by PGE(1) to diffuse to L-type Ca2+ channels. These results identify specific functional coupling of individual PDE families to G(s)-coupled receptors as a major mechanism enabling cardiac cells to generate heterogeneous cAMP signals in response to different hormones.