“We’ve focused for many years on the nitric oxide pathway to find new therapies that might improve outcomes for babies with pulmonary hypertension,” Aschner said. In the body, the enzyme nitric oxide synthase (NOS) produces nitric oxide from the amino acid arginine. Aschner and colleagues had discovered that NOS is present in a multi-protein complex, which is important for the activation of NOS and production of nitric oxide.