Objective: To explore the effect of prolonged nitric oxide (NO) inhalation on chronically hypoxic rats.
Methods: Male Wistar rats were randomly divided into 3 groups: 1) room-air control (C); 2) hypoxia (H); 3) hypoxia with the inhalation of 20 ppm NO(2NH). RV/LV + S, mPAP and the histopathology of the lung were examined. Plasma levels of ET-1 and cGMP were detected by radioimmunoassay.
Results: 1. Hypoxia caused marked elevation in mPAP and RV/LV + s (both P < 0.001 vs Group C). NO significantly reduced mPAP and RV/LV + S; 2. Hypoxia raised the percentage of intra-acinar muscular artery (MA) and lowered that of nonmuscular artery (NAM). MA decreased from 35.2% to 16.8% in Group 2NH; NMA increased from 43.6% to 64.8% in Group 2NH, 3. The plasma level of ET-1 increased and that of cGMP droped significantly in Group H(both P < 0.001 vs Group C). NO resulted in a marked reduction in the plasma ET-1 and an increase in plasma cGMP; 4. Inhalation of NO had no effect on methemoglobin and lung index in hypoxic rats.
Conclusions: Prolonged inhalation of 20 ppm NO can attenuate hypoxic pulmonary hypertension and inhibit the hypertrophy of the pulmonary vascular smooth muscle and the right ventricle NO, when inhalated at a concentration of 20 ppm for a long duration, will cause no toxicity in chronically hypoxic rats.