ENTPD1 and chronic obstructive pulmonary disease: Densitometric analyses of the bands showed that CD39 band density was lower in the COPD group (0.34 [0.22–0.92]) compared with the NOS group (0.67 [0.32–1.06]) and the NS group (0.95 [0.4–1.1]) (Fig. 3; p = 0.133).