Interaction between en- dogenous nitric oxide and carbon monoxide in the pathogenesis of hypoxic pulmonary hypertension
Interaction between endogenous nitric oxide and carbon monoxide in the pathogenesis of hypoxic pulmonary hypertension

The aim of the study was to investigate the in-teraction between nitric oxygenase (NOS)/ nitric oxide (NO) and heme oxygenase (HO)/ carbon monoxide (CO) system in the pathogenesis of hypoxic pulmonary hypertension. On a rat model of hypoxic pulmonary hypertension, the pulmo-nary artery pressure was measured, and NO formation and expression of NOS in pulmonary tissues were examined after treatment with ZnPP-IX, an HO-1 inhibitor. The pulmonary artery pressure, CO formation and expression of HO-1 in pulmonary tissues were examined after treatment with L-NAME, a NOS inhibitor. We found that pulmonary hy-pertension developed after 2-week hypoxia, while the con-centration of NO in the pulmonary tissue homogenates and the expression of NOS in intrapulmonary artery endothelial cells decreased markedly. ZnPP-IX worsened pulmonary hypertension of hypoxic rats. However, it increased endoge-nous production of NO and the expression of NOS obviously. The concentration of CO in the pulmonary tissue homoge-nates and the expression of HO-1 in intrapulmonary artery smooth muscle cells increased markedly with hypoxic pul-monary hypertension. L-NAME worsened pulmonary hy-pertension of hypoxic rats, but inhibited CO formation and HO-1 expression (P < 0.01). The results of this study sug-gested that endogenous NOS/NO and HO/CO systems might interact with each other and therefore play an important regulating role in hypoxic pulmonary hypertension.