Expression and activity of low Km, cGMP-inhibited cAMP phosphodiesterase in cardiac and skeletal muscle

The expression and activity of low Km, cGMP-inhibited cAMP phosphodiesterase (PDE3)4 were examined in rabbit and canine cardiac and skeletal muscle. In cardiac muscle, a cDNA probe whose sequence encompasses the catalytic domain of human myocardial PDE3 (PDE3A) hybridized predominantly with a 7.2-7.4 kb mRNA. No hybridization was observed in preparations from slow or fast twitch skeletal muscle. Likewise, PDE3 activity was present in cytosolic and microsomal fractions of cardiac muscle but was absent from cytosolic and microsomal fractions of slow twitch and fast twitch skeletal muscle. These results, which demonstrate the absence of PDE3 from slow and fast twitch mammalian skeletal muscle, further delineate the differences in beta-adrenergic receptor-mediated signal transduction pathways in cardiac and skeletal muscle.