Inhaled nitric oxide effects on lung structure and function in chronically ventilated preterm lambs.
BACKGROUND
Inhaled nitric oxide (iNO) can reverse neonatal pulmonary hypertension and bronchoconstriction and reduce proliferation of cultured arterial and airway smooth muscle cells.


OBJECTIVE
To see if continuous iNO from birth might reduce pulmonary vascular and respiratory tract resistance (PVR, RE) and attenuate growth of arterial and airway smooth muscle in preterm lambs with chronic lung disease.


METHODS
Eight premature lambs received mechanical ventilation for 3 weeks, four with and four without iNO (5-15 ppm). Four term lambs, mechanically ventilated without iNO for 3 weeks, served as additional control animals.


METHODS
PVR and RE were measured weekly. After 3 weeks, lung tissue was processed for quantitative image analysis of smooth muscle abundance around small arteries (SMart) and terminal bronchioles (SMtb). Radial alveolar counts were done to assess alveolar number. Endothelial NO synthase (eNOS) protein in arteries and airways was measured by immunoblot analysis.


RESULTS
At study's end, PVR was similar in iNO-treated and untreated preterm lambs; PVR was less in iNO-treated preterm lambs compared with term control animals. RE in iNO-treated lambs was less than 40% of RE measured in preterm control animals. SMart was similar in iNO-treated and both groups of control lambs; SMtb in lambs given iNO was significantly less (approximately 50%) than in preterm control animals. Radial alveolar counts of iNO-treated lambs were more than twice that of preterm control animals. eNOS was similar in arteries and airways of iNO-treated preterm lambs compared with control term lambs.


CONCLUSIONS
iNO preserves structure and function of airway smooth muscle and enhances alveolar development in preterm lambs with chronic lung disease.
Department of Pediatrics, Stanford University School of Medicine, CCSR Building, Room 1225, 269 Campus Drive, Stanford, CA 94305-5162, USA. rbland@stanford.edu
Richard D
RD
Bland
Kurt H
KH
Albertine
David P
DP
Carlton
Amy J
AJ
MacRitchie
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D002908:Chronic Disease; D004195:Disease Models, Animal; D007091:Image Processing, Computer-Assisted; D008171:Lung Diseases / Q000503:physiopathology*; D009130:Muscle, Smooth / Q000187:drug effects; D009569:Nitric Oxide / Q000494:pharmacology*; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000502:physiology; D012119:Respiration / Q000187:drug effects*; D012121:Respiration, Artificial; D012756:Sheep
D009569:Nitric Oxide