[Effect of prolonged inhalation of nitric oxide on chronically hypoxic rats].

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.