Introduction: All three isoforms of nitric oxide synthase (NOS) are identified within various tissues of the respiratory system.
Isoforms of nos: Under physiological conditions, small amounts of NO, produced by constitutive isoforms of NOS, appear to be important in regulation of basal pulmonary vascular tone and in mediating transition from fetal to neonatal circulation; also, NO exerts antiinflammatory actions, and modulates the respiratory smooth muscle tone. NO AND RESPIRATORY TRACT DISEASES: Under pathological conditions, inducible NOS-derived NO may produce lung damage. In addition, increased or decreased production of NO is found in chronic obstructive pulmonary disease, cystic fibrosis, asthma and related inflammatory disorders, and exhaled NO level measurement is a useful tool in diagnostics of respiratory disorders.
Conclusion: It has been shown that NO modulates contractility of the isolated diaphragm, and there are important interactions between NOS inhibitors and drugs for respiratory disorders (e.g. aminophylline).