Compartmentation of β -adrenoceptor stimulated cAMP responses by phosphodiesterase types 2 and 3 in cardiac ventricular myocytes.

Background And Purpose: In cardiac myocytes, cyclic AMP (cAMP) produced by both β - and β -adrenoceptors increases L-type Ca channel activity and myocyte contraction. However, only cAMP produced by β -adrenoceptors enhances myocyte relaxation through phospholamban-dependent regulation of the sarco/endoplasmic reticulum Ca ATPase 2 (SERCA2). Here we have tested the hypothesis that stimulation of β -adrenoceptors produces a cAMP signal that is unable to reach SERCA2 and determine what role, if any, phosphodiesterase (PDE) activity plays in this compartmentation.