eNOS and prostanoid enzymes in lungs of newborn piglets with chronic aortopulmonary shunts

Our purpose was to determine if abundance of proteins underlying nitric oxi de (NO) and prostanoid production is altered in lungs of piglets with aorto pulmonary shunts. We also evaluated whether shunted piglets exhibit abnorma l pulmonary vascular responses to ACh, an endothelium-dependent agent that mediates dilation in part by NO and prostanoid release. At age 4-5 days, pi glets underwent either a sham operation or placement of an aortopulmonary s hunt. At age 5-6 wk, pulmonary arterial pressure (Ppa) and cardiac output b y the thermodilution technique were measured in anesthetized piglets. Ppa r esponses to the endothelium-dependent agent, ACh, and to a non-endothelium- dependent agent, papaverine, were measured in perfused lungs. An immunoblot technique was applied to homogenates of whole lung tissue and two size gro ups of pulmonary arteries. In shunted piglets, Ppa and cardiac output were elevated, and Ppa responses to papaverine were reduced. ACh responses were not decreased when expressed relative to Ppa dilation with papaverine. Endo thelial nitric oxide synthase (eNOS), cyclooxygenase-1, cyclooxygenase-2, p rostacyclin synthase, and thromboxane synthase amounts were unaltered in al l lung tissue homogenates. Altered abundance of eNOS and/or prostanoid enzy mes does not contribute to the blunted dilation and the elevation in Ppa as sociated with aortopulmonary shunts in newborn piglets.