Gordon John B, VanderHeyden Michele A, Halla Ted R, Cortez Edmundo P, Hernandez Guillermo, Haworth Steven T, Dawson Christopher A, Madden Jane A
Department of Pediatrics (Critical Care), Medical College of Wisconsin and Zablocki Veterans Administration Medical Center, Milwaukee, Wisconsin 53226, USA.
Am J Physiol Lung Cell Mol Physiol. 2003 May;284(5):L799-807. doi: 10.1152/ajplung.00402.2002. Epub 2003 Jan 24.
We previously found that nitric oxide synthase (NOS) inhibition fully blocked alkalosis-induced relaxation of piglet pulmonary artery and vein rings. In contrast, NOS inhibition alone had no effect on alkalosis-induced pulmonary vasodilation in isolated piglet lungs. This study sought to identify factors contributing to the discordance between isolated and in situ pulmonary vessels. The roles of pressor stimulus (hypoxia vs. the thromboxane mimetic U-46619), perfusate composition (blood vs. physiological salt solution), and flow were assessed. Effects of NOS inhibition on alkalosis-induced dilation were also directly compared in 150-350-microm-diameter cannulated arteries and 150-900-microm-diameter, angiographically visualized, in situ arteries. Finally, effects of NOS inhibition on alkalosis-induced vasodilation were measured in intact piglets. NOS inhibition with N(omega)-nitro-L-arginine fully abolished alkalosis-induced vasodilation in all cannulated arteries but failed to alter alkalosis-induced vasodilation in intact lungs. The results indicate that investigation of other factors, such as perivascular tissue (e.g., adventitia and parenchyma) and remote signaling pathways, will need to be carried out to reconcile this discordance between isolated and in situ arteries.
