title: Acute phosphodiesterase 5 inhibition mimics hemodynamic effects of B-type natriuretic peptide and potentiates B-type natriuretic peptide effects in failing but not normal canine heart.
abstract: OBJECTIVE
  The aim of this work was to test whether acute phosphodiesterase 5 (PDE5) inhibition via sildenafil (SIL) mimics and/or potentiates cardiorenal effects of exogenous natriuretic peptide (NP) infusion.
  
  
  BACKGROUND
  Heart failure (HF) is often accompanied by elevated NP secretion yet blunted responsiveness. Such NP resistance may, in part, relate to increased cyclic guanosine monophosphate (cGMP) catabolism by PDE5.
  
  
  METHODS
  Dogs (n = 7) were studied before and after tachypacing-induced HF. Animals received 30-min infusion of B-type natriuretic peptide (BNP) (2 mug/kg bolus, 0.02 mug/kg/min), and on a separate day SIL (1 mg/kg, intravenous), followed by BNP (SIL + BNP). Phosphodiesterase 5 activity was measured in lung, vasculature, and kidney.
  
  
  RESULTS
  At baseline (non-failing), BNP lowered central venous, pulmonary capillary wedge, diastolic, mean pulmonary artery, and mean arterial pressure. Sildenafil had no effects, and SIL + BNP was similar to BNP alone. In contrast, SIL lowered these pressures similarly to BNP in dogs with HF, and SIL + BNP was additive in further reducing pulmonary pressures over BNP alone. Plasma cGMP/plasma BNP ratio was markedly reduced with HF, indicating NP resistance. Sildenafil plus BNP increased this ratio in HF, but had no effect in non-failing animals. Sildenafil had no independent diuretic/natriuretic effects nor did it enhance BNP effects under baseline or HF conditions. In HF, PDE5 activity was significantly increased in the systemic and pulmonary vasculature and in the kidney.
  
  
  CONCLUSIONS
  The PDE5 activity in systemic and pulmonary vasculature increases in HF rendering hemodynamic responses to PDE5 inhibition identical to those from BNP infusion. Natriuretic peptide desensitization in HF relates, in part, to increased PDE5 activity, supporting a therapeutic role for PDE5 inhibition.
authors.affiliation: Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland 21205, USA.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Forfia
authors.forename: Myung
authors.initials: M
authors.lastname: Lee
authors.forename: Richard S
authors.initials: RS
authors.lastname: Tunin
authors.forename: Mobusher
authors.initials: M
authors.lastname: Mahmud
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*; D000818:Animals; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D004195:Disease Models, Animal; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004357:Drug Synergism; D005260:Female; D006333:Heart Failure / Q000188:drug therapy*; D007262:Infusions, Intravenous; D008297:Male; D015999:Multivariate Analysis; D020097:Natriuretic Peptide, Brain / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011336:Probability; D011687:Purines / Q000494:pharmacology; D011897:Random Allocation; D012016:Reference Values; D012307:Risk Factors; D012680:Sensitivity and Specificity; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000494:pharmacology*
chemical_list: D010879:Piperazines; D011687:Purines; D013450:Sulfones; D020097:Natriuretic Peptide, Brain; D000068677:Sildenafil Citrate; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5