Objective To investigate the relationship among the levels of plasma endothelin-1( ET-1),nitric oxide synthase( NOS) and the pulmonary artery systolic pressure in the patients with the stable period of chronic obstructive pulmonary disease( COPD). Methods The patients with the stable period of COPD were collected and divided into Hui group and Han group. Normal subjects were chosen to be the controls. The levels of plasma ET-1 and NOS were detected and compared among the three groups.Results Compared with t...