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Abstract

The hemodynamic responses to terbutaline – a selective β2-adrenoceptor agonist – were studied in conscious normal rats and in conscious rats with secondary biliary cirrhosis. Compared with those of normal rats, dose-response curves in cirrhotic rats indicated significantly decreased reactivity in arterial pressure and heart rate. Half-maximal effective dose was not significantly different between the two groups. Terbutaline induced significant, dose-dependent decreases in portal pressure in both normal rats (9.3%) and cirrhotic rats (13.8%). In normal rats, terbutaline administration (32 μg ± min−1 ± kg−1 body wt) increased both cardiac output and portal tributary blood flow, thus mimicking hemodynamic changes in cirrhotic rats. In cirrhotic rats, despite a significant increase in portal tributary blood flow (from 19.9 ± 1.7 ml/min to 22.7 ± 1.5 ml/min), terbutaline decreased portal pressure from 17.4 ± 1.0 mm Hg to 15.0 ± 0.8 mm Hg. This study indicates that increased β2-adrenoceptor stimulation in cirrhotic rats may be involved in hyperdynamic circulation. The association of a decreased portal pressure and increased splanchnic blood flow suggests that β2-adrenoceptor stimulation may modulate hepatic and portal collateral vascular resistance. (Hepatology 1992;15:459–463).