Manihot esculenta

Abstract

Objective To study the effect of chronic beta1-selective blockor treatment on beta-adrenoreceptor subtypal function in human. Methods Cardiac beta1-adrenoreceptor subtypes responsiveness were measured by treadmill exercise test and cardiac beta2-adrenoreceptor responsiveness by salbutamol injection test in 20 male patients with essential hypertension (EH) after beta1-selective blockor treatment for at least 4 months and withdrawal for 3 days. The twenty male patients with EH and non-beta-blockors treatment for at least 4 months were used as controls. Results The increases in peak exercise heart rate by treadmill were not significantly different between the patients with beta1-blockor treatment and those with non-beta-blockor treatment. The chronotropic dose of salbutamol that increased heart rate by 30 beats/min [chronotropic dose 30 (CD30)] in [beta1-blockor treatment group were significantly lower than those in non-beta-blockor treatment group (1.8 +/- 0.3 vs 2.7 +/- 0.2 mug/kg, P < 0.001). Blood pressures did not change significantly after salbutamol injection in both groups. Conclusion The treatment with beta1-selective blockor leads to cross sensitisation of cardiac beta2-adrenoreceptor in human. This is the possible celluological mechanism of the beta-blockor withdrawal syndrome.