The Role of NO Synthase in the Infarct-Limiting Effect of Urgent and Chronic Adaptation to Normobaric Hypoxia

We studied the role of NO synthase in the infarct-limiting effect of short-term (SNH) and chronic continuous normobaric hypoxia (CNH). In male Wistar rats, SNH (6 sessions of 10-min hypoxia 8% O2 and 10-min reoxygenation) or CNH (12% O2 for 21 days) was modeled. In 30 min after SNH or 24 h after CNH, the rats were subjected to coronary artery occlusion (45 min) and reperfusion (2 h). The following drugs were administered to rats: non-selective NO synthase inhibitor L-NAME (10 mg/kg), inhibitor of inducible NO synthase S-methylthiourea (3 mg/kg), and inhibitor of neuronal NO-synthase 7-nitroindazole (50 mg/kg). NO donor diethylenetriamine was administered intravenously in a dose 2 mg/kg. It was found that L-NAME and S-methylthiourea abolished the infarct-limiting effect of SNH and CNH. Diethylenetriamine increased cardiac tolerance to ischemia/reperfusion. It is believed that inducible NO synthase plays an important role in the cardioprotective effect of normobaric hypoxia.