Inhibition of lung phosphodiesterase improves responsiveness to inhaled nitric oxide in isolated-perfused lungs from rats challenged with endotoxin.
OBJECTIVE
To investigate the ability of phosphodiesterase (PDE) selective inhibitors to improve responsiveness to inhaled nitric oxide (NO) in isolated-perfused lungs of rats pretreated with endotoxin/lipopolysaccharide (LPS).


METHODS
Prospective, controlled animal study in the animal research facility of a university hospital.


METHODS
Sixteen hours after adult Sprague-Dawley rats were injected intraperitoneally with 0.4 mg/ kg E. coli 0111:B4 LPS administration, lungs were isolated and perfused, and the thromboxane mimetic U46619 was employed to increase the mean pulmonary artery pressure by 5-7 mmHg. The lungs were then ventilated with or without 0.4 ppm NO, and erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA; PDE type 2 inhibitor), milrinone (PDE type 3 inhibitor), or zaprinast (inhibitor of PDE types 5 and 9) were added to the perfusate.


RESULTS
In the presence of EHNA (12.5, 25, 50 microM) the vasodilator response to inhaled NO was not greater than in its absence (0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg vs. 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg, respectively). In the presence of milrinone (125, 250, 500 nM), the vasodilator response to inhaled NO was also not improved. In contrast, zaprinast (3.7, 7.4, 14.8 microM) augmented the pulmonary vasodilatory effect of inhaled NO in lungs from LPS-pretreated rats from 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg to 0.75 +/- 0.25, 1.5 +/- 0.5, 1.75 +/- 0.75 mmHg, respectively (p < 0.05).


CONCLUSIONS
Our results demonstrate that inhibition of pulmonary PDE enzyme activity with zaprinast increases vasodilator responsiveness to inhaled NO in lungs obtained from rats 16 h after LPS challenge.
Department of Anaesthesiology, University of Heidelberg, Germany.
A
A
Holzmann
C
C
Manktelow
J
J
Weimann
K D
KD
Bloch
W M
WM
Zapol
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D008070:Lipopolysaccharides; D020105:Milrinone / Q000494:pharmacology; D015999:Multivariate Analysis; D009569:Nitric Oxide / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D011688:Purinones / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012128:Respiratory Distress Syndrome / Q000139:chemically induced / Q000188:drug therapy*; D014664:Vasodilation / Q000187:drug effects*
D008070:Lipopolysaccharides; D010726:Phosphodiesterase Inhibitors; D011688:Purinones; D009569:Nitric Oxide; C011145:zaprinast; D020105:Milrinone