Effects of β-adrenoceptor activation on hemodynamics in hypoxic stress rats.

NEW FINDINGS What is the central question of this study? Acute hypoxic compensatory reaction is accompanied by hemodynamic changes, and β-adrenoceptor is involved in the regulation of hemodynamics. However, the role of β-adrenoceptor on hemodynamics in hypoxic exposure is still not clear and remains to be investigated. What is the main finding and its importance? The activation of β2 -adrenoceptor attenuates the increase in pulmonary artery pressure under hypoxic exposure. This compensatory reaction activated by β2 -adrenoceptor under hypoxia stress is very important to maintain normal life activities. ABSTRACT Acute hypoxic compensatory reaction is accompanied by hemodynamic changes. In this study, we monitored the hemodynamic changes in rats under acute hypoxic stress by applying different subtypes of β-adrenoceptor (β-AR) antagonists to reveal the regulatory role of β-AR on hemodynamics. Sprague-Dawley rats were randomly divided into control, atenolol (β1 -AR antagonist), ICI 118,551 (β2 -AR antagonist), and propranolol (nonselective β-AR antagonist) groups. Rats were continuously recorded for changes in hemodynamic indexes within 10 minutes after administration. Then, a hypoxic ventilation experiment (15 % O2 , 2200 meters, 582 mmHg, 87.3 mmHg PO2 , Xining, China) was conducted, and the indexes were monitored within 5 minutes after induction of hypoxia. In addition, plasma catecholamine concentration was measured. Our results showed that, under normoxia, the mean arterial pressure (MAP), heart rate (HR), ascending aorta blood flow (ABF), and pulmonary artery pressure (PAP) were decreased in the propranolol and atenolol groups. The concentration of catecholamine was increased significantly in the atenolol group compared with control group. Under hypoxia, MAP and total peripheral resistance (TPR) were decreased in the control, propranolol, and ICI 118,551 groups. The PAP and pulmonary vascular resistance (PVR) were increased in the propranolol and ICI 118,551 groups. Under hypoxia, the concentration of catecholamine was increased significantly in the control group, while was decreased in the β-AR antagonist groups. In conclusion, β2 -AR is involved in the regulation of pulmonary hemodynamics in acute hypoxic compensatory reaction, and the activation of β2 -AR attenuates the increase in PAP under hypoxic stress. This compensatory reaction activated by β2 -adrenoceptor under hypoxia stress is very important to maintain normal life activities. This article is protected by copyright. All rights reserved.