内源性一氧化氮（NO）是一种活性很强的自由基，既是细胞信使分子，又是细胞毒性分子．因此，NO的自由基活性对哮喘发病机制的影响越来越受到重视。在体内，一氧化氮合成酶（NOS）是催化生成NO最重要的关键酶．NOS分为两种，即诱导型NOS（iNOS）和原生型NOS（NOS）。不同的酶产 Endogenous nitric oxide (NO) is a highly active free radical, both a cellular messenger molecule and a cytotoxic molecule. Therefore, the effect of free radical activity of NO on the pathogenesis of asthma has drawn more and more attention. In the body, nitric oxide synthase (NOS) is the key enzyme that catalyzes the production of NO. NOS is divided into two types, namely, inducible NOS (iNOS) and native NOS (NOS). Different enzyme production