title: Compartmentalization of cardiac beta-adrenergic inotropy modulation by phosphodiesterase type 5.
abstract: BACKGROUND
  Recent cell-based studies have found that cGMP synthesis and hydrolysis by phosphodiesterase (PDE) appear compartmentalized, with nitric oxide synthase-derived and/or PDE type 5 (PDE-5)-hydrolyzable cGMP undetected at the sarcolemmal membrane in contrast to cGMP stimulated by natriuretic peptide. In the present study, we determine the functional significance of such compartments with a comparison of beta-adrenergic modulation by PDE-5 inhibition to that of natriuretic peptide stimulation in both cardiomyocytes and intact hearts. The potential role of differential cGMP and protein kinase G stimulation by these 2 modulators was also studied.
  
  
  RESULTS
  Intact C57/BL6 mouse hearts were studied with pressure-volume analysis, and adult isolated myocytes were studied with fluorescence microscopy. PDE-5 inhibition with 0.1 to 1 micromol/L sildenafil (SIL) suppressed isoproterenol (ISO)-stimulated contractility, whereas 10 micromol/L atrial natriuretic peptide (ANP) had no effect. ISO suppression by SIL was prevented in cells pretreated with a protein kinase G inhibitor. Surprisingly, myocardial cGMP changed little with SIL+ISO yet rose nearly 5-fold with ANP, whereas protein kinase G activation (vasodilator-stimulated protein phosphorylation; ELISA assay) displayed the opposite: increased with SIL+ISO but unaltered by ANP+ISO. PDE-5 and ANP compartments were functionally separated, as inhibition of nitric oxide synthase by N(w)-nitro-L-arginine methyl ester eliminated antiadrenergic effects of SIL, yet this was not restorable by co-stimulation with ANP.
  
  
  CONCLUSIONS
  Regulation of cardiac beta-adrenergic response by cGMP is specifically linked to a nitric oxide-synthesis/PDE-5-hydrolyzed pool signaling via protein kinase G. Natriuretic peptide stimulation achieves greater detectable increases in cGMP but not protein kinase G activity and does not modulate beta-adrenergic response. Such disparities likely contribute to differential cardiac regulation by drugs that modulate cGMP synthesis and hydrolysis.
authors.affiliation: Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21205, USA.
authors.forename: Eiki
authors.initials: E
authors.lastname: Takimoto
authors.forename: Diego
authors.initials: D
authors.lastname: Belardi
authors.forename: Carlo G
authors.initials: CG
authors.lastname: Tocchetti
authors.forename: Susan
authors.initials: S
authors.lastname: Vahebi
authors.forename: Gianfrancesco
authors.initials: G
authors.lastname: Cormaci
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Ketner
authors.forename: An L
authors.initials: AL
authors.lastname: Moens
authors.forename: Hunter C
authors.initials: HC
authors.lastname: Champion
authors.forename: David A
authors.initials: DA
authors.lastname: Kass
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000502:physiology*; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D002451:Cell Compartmentation / Q000502:physiology; D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured / Q000187:drug effects / Q000502:physiology; D006152:Cyclic GMP / Q000502:physiology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D006162:Guanylate Cyclase / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011687:Purines / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D015290:Second Messenger Systems / Q000502:physiology; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000494:pharmacology*
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011687:Purines; D011943:Receptors, Adrenergic, beta; D013450:Sulfones; D009569:Nitric Oxide; D009320:Atrial Natriuretic Factor; D000068677:Sildenafil Citrate; D017869:Cyclic GMP-Dependent Protein Kinases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517382:Pde5a protein, mouse; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D007545:Isoproterenol; D019331:NG-Nitroarginine Methyl Ester