Inhibition of Expression of Hypoxia-inducible Factor-1α mRNA by Nitric Oxide in Hypoxic Pulmonary Hypertension Rats

In order to study the effect of nitric oxide (NO) on the expression of hypoxia inducible factor 1 alpha (HIF 1α) mRNA in hypoxic pulmonary hypertension (HPH) rats, 30 healthy male Wistar rats were randomly divided into normoxic control group, chronic hypoxic group and hypoxia plus L argine (L Arg) group. The animal model of HPH was developed. The mean pulmonary arterial pressure (mPAP) was measured by inserting a microcatheter into the pulmonary artery. The HIF 1α mRNA expression levels were detected by in situ hybridization (ISH) and semiquantitative RT PCR. It was found that after 14 days hypoxia, the mPAP in normoxic control group (17.6±2 7 mmHg,1 mmHg=0 133 kPa) was significantly lower than that in chronic hypoxic group(35.8±6.1 mmHg, t =0.2918, P <0.05) and mPAP in chronic hypoxic group was higher than that in hypoxia plus L argine group(24.4±3.8 mmHg, t =0.2563, P <0.05). ISH showed that the expression of HIF 1α mRNA in the intraacinar pulmonary arteriolae (IAPA) in normoxic control group (0.1076±0.0205) was markedly weaker than that in chronic hypoxic group (0.3317±0.0683, t =3.125, P <0.05) and that in chronic hypoxic group was stronger than that in hypoxia plus L argine group (0.1928±0.0381, t =2.844, P <0.05). RT PCR showed that the content of HIF 1α mRNA in chronic hypoxic group (2.5395±0.6449) was 2.16 times and 1.75 times higher than that in normoxic control group (1.1781±0.3628) and hypoxia plus L argine group (1.4511±0.3981), respectively. It is concluded that NO can reduce the mPAP by the inhibition of the expression of HIF 1α mRNA, which may be one of the mechanisms through which NO affects the pathogenesis of HPH.