[Changes of nitric oxide synthase in hypoxic pulmonary hypertension and the effect of L-arg and L-NAME on pulmonary circulation].

OBJECTIVE

To study the role of nitric oxide (NO) in Hypoxic pulmonary hypertension (HPH).

METHODS

NADPH-d and immunohistochemistry were used to study the expression and localization of constructive and inducible nitric oxide synthase (cNOS iNOS) in the lungs of normoxia and HPH rats, at the same time, the effects of L-arginine (L-arg) and nitro-L-arginine-methyl-ester (L-NAME) on normoxic and hypoxic pulmonary circulation were investigated.

RESULTS

NADPH-d positive expression was detected in the endothelium and smooth muscle cells (SMC) of large pulmonary vessels (PV) and in the epithelium and SMC of bronchi in the HPH group, but negative in the endothelium and SMC of small PV in normoxia. Hypoxia not only inhibited the expression of cNOS in the endothelium and SMC of PV and epithelium of bronchi, but also induced the expression of iNOS in the endothelium and SMC of PV and SMC of bronchi. Administration of L-NAME in normoxia had no effect on pulmonary circulation. The effect of administration of L-arg and L-NAME in hypoxia on right ventricular hypertrophy and remodeling of PV had no significance, compared with simple hypoxia.

CONCLUSION

The inhibition of cNOS may contribute to the occurrence of HPH, but induced iNOS may depress the development of HPH.