Aim: To investigate the dynamic changes and functions of urotensin II (U lI) receptor (UT) in pulmonary arteries of rats chronically exposed to hypoxia-hypercapnia.
Methods: In rats with hypoxia-hypercapnia at 1, 2 and 4 weeks U II receptor binding of pulmonary arteries sarcolemma was determined by radioligand assay. U II mRNA and UTmRNA in various grades of pulmonary arterioles were measured by in situ hybridization.
Results: (1) Mean pulmonary pressure (mPAP) and weight ratio of right ventricle to left ventricle and septum (RV/LV + S) of 1-week group were higher than those of normal control (NC) group by 26.2% and 21.6% (P < 0.01), respectively, and 2-week group higher than 1-week group by 22.5% and 14.1% (respectively, P < 0.01). However, no significant changes were found between 4-week and 2-week group. (2) U Il receptor (Bmax) of 1-week group was higher than NC group by 38.8%, 2-week group higher than 1-week group by 23.2%, and 4-week group increased 7.3% compared with 2-week group (respectively, P < 0.01). The UT changes were time-dependent, while the affinity to U II (Kd) was no different among each group. (3) UII mRNA in each grade of pulmonary arterioles of 2-week group and 4-week group were higher than NC group (respectively, P < 0.01), and those of 2-week group were higher than 1-week group by 5.9% (P > 0.05), 16.4% and 9.1% (respectively, P < 0.01), while no differences existed between 2-week group and 4-week group. (4) UT mRNA in each grade of pulmonary arterioles of all hypoxia-hypercapnia groups was higher than NC group (respectively, P < 0.01), and those of two abaxial grade vessels in 1-week group were the highest. No differences existed between 2-week group and 4-week group. (5) The pulmonary vessels remodeling were time-dependently aggravated by hypoxia-hypercapnia.
Conclusion: The dynamic changes of UT in pulmonary arterioles might have important contribution to the development of pulmonary hypertension and pulmonary arteriole remodeling induced by chronic hypoxia-hypercapnia in rats.