Reduction in protein levels of MYPT1 of porcine pulmonary arteries caused by incubation with DETA NO (10−4 M) was prevented when 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ; 3 × 10−5 M) was presented in the incubation medium. Top, Western blots; bottom, summaries of densitometric scanning of MYPT1 protein normalized to actin. Data are means ± SE; n = 4–6 for each group. *P < 0.05, significantly different from control.