OBJECTIVETo study the role of apelin in the prevention of pulmonary hypertension induced by hypoxia in rats.

METHODSThe animal model of hypoxic pulmonary hypertension was established by exposing the rats to isobaric hypoxic chamber for 4 weeks (8 h/d, 6 d/ w). Forty male Sprague-Dawley rats were randomly divided into control group (NC), hypoxic group(HH), hypoxic with low-dose apelin (5 nmol/(kg x d) group(LA) and high-dose apelin (10 nmol/(kg x d) (HA). [pGlu]apelin-13 was administered into the rats of apelin groups by mini-osmotic pump subcutaneously. The mean pulmonary arterial pressure(mPAP) and the mean carotid arterial pressure (mCAP) were measured by either right or left cardiac catheterization, and the weight ratio of right ventricule/left ventricule plus septum (RV/(LV + S)) were calculated. The Masson's trichrome stained lung specimens were examined by light microscope to examine the vessel wall area/total area (WA/TA), vessel cavity area/total area (CA/TA) and media thickness of pulmonary arterioles (PAMT). Meanwhile, the lung homogenates were assayed for the activity of supeeroxide dismutase (SOD) and the content of malondialdehyde (MDA).

RESULTS(1) mPAP and RV/(LV + S) of HH group were significantly higher than those of NC group. mPAP of LA and HA groups were lower than those of HH group. The RV/(LV + S) of HA group was significantly lower than that of HH group, but there was no significant difference between HH group and LA group. (2) Masson's trichrome staining revealed that WA/TA and PAMT of HH group were higher than those of NC group. Administration of apelin significantly eliminated WA/TA and PAMT in LA and HA groups. (3) CA/TA of HH group was lower than that of NC group. Administration of apelin significantly elevated CA/TA in LA and HA groups. (4) The activity of SOD and content of MDA in HH group was, respectively, lower and higher than those in NC group. Apelin treatment increased the activity of SOD in LA and HA groups while decreased the content of MDA.

CONCLUSIONSApelin could play an important role in treatment of hypoxic pulmonary hypertension of rats and the mechanisms of protection were associated with vasodilation of pulmonary artery and inhibition of oxidative stress.