Location and Expression of 5-HT1B Receptor in Lung Tissue of Rats with Hypoxic Pulmonary Hypertension

Objective:To investigate the changes of location and expression of 5-HT1B receptor in lung tissue of hypoxic pulmonary hypertension rats and to explore the mechanisms of hypoxic pulmonary hypertension(HPH).Methods:Forty male Sprague-Dawley rats were randomly divided into 4 groups:normoxia control(control),3w hypoxia(3w),4w hypoxia(4w) and 5w hypoxia(5w).The rats in normoxia control stayed in normal environment.The rats in 3w hypoxia,4w hypoxia and 5w hypoxia had been kept respectively in hypoxia chamber for 3 weeks,4 weeks and 5 weeks to establish the HPH animal model.After HPH rats were established,The mean pulmonary pressure(mPAP) and the right ventricular systolic pressure(RVSP) were recorded by a micro-catheter.RV/(LV + S) ratio was calculated to assess right vetricular hypertrophy.Location and expression of 5-HT1B receptor in lung tissues were measured by immunohistochemical and Western blot analyses.Results:Compared with normoxia control,mPAP,RVSP and RV/(LV + S)% of 3w hypoxia rats increased significantly(P 0.05),which continued to increase following prolonged hypoxia.Immunohistochemistry shows that 5-HT1B receptor is localized mainly in the intima of the pulmonary arteries in normal rats.Exposed to hypoxia,immunoreactivity for 5-HT1B receptor increased in the media of 3w hypoxia rats' pulmonary arteries,particularly those bordering the adventitia.There were more changes in the expressions of 5-HT1B receptor following prolonged hypoxia.Western blot result showed the same changes of 5-HT1B receptor expressions in the lung tissues as that of 5-HT1B immunoreactivity in pulmonary arteries.Conclution:Hypoxia can induce the over-expression of 5-HT1B receptor in HPH rats' pulmonary arteries.It may be one of the underlying mechanisms of the development of HPH.