Nitric oxide synthase in pulmonary hypertension: Lessons from knockout mice

Nitric oxide (NO) is implicated in a wide variety of biological roles. NO i s generated fi-om three nitric oxide synthase (NOS) isoforms: neuronal (nNO S), inducible (iNOS), and endothelial (eNOS) all of which are found in the lung. While there are no isoform-specific inhibitors of NOS, the recent dev elopment and characterization of mice deficient in each of the NOS isoforms has allowed for more comprehensive study of the importance of NO in the lu ng circulation. Studies in the mouse have identified the role of NO from eN OS in modulating pulmonary vascular tone and in attenuating the development of chronic hypoxic pulmonary hypertension.