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Hemodynamic responses to selective blockade of beta 2- and beta 1-adrenoceptors in conscious rats with cirrhosis.

This study examined the hemodynamic effects of selective beta 2-adrenergic blockade (ICI 118,551, 100 micrograms/kg intravenous (i.v.)), selective beta 1-blockade (atenolol, 2 mg i.v.) and nonselective beta-blockade (propranolol, 2 mg i.v.) in conscious rats with cirrhosis. Pressure and blood flow measurements (radioactive microsphere method) were performed before and following drug administration. ICI 118,551 significantly decreased portal tributary blood flow (21%), portal pressure (4%) and cardiac index (12%). Portal tributary blood flow decreases were significantly more marked than changes in cardiac index. Atenolol significantly decreased portal tributary blood flow (27%), portal pressure (15%), cardiac index (17%) and arterial pressure (7%). Propranolol significantly decreased portal tributary blood flow (37%), portal pressure (17%), cardiac index (30%), and arterial pressure (9%). Portal tributary blood flow decreases due to ICI 118,551, but not those due to atenolol, were significantly less marked than the decreases caused by propranolol. ICI 118,551- and atenolol-induced cardiac index decreases were significantly less marked than propranolol-induced decreases. In conclusion, in rats with cirrhosis, selective beta 2-blockade reduces portal pressure and portal tributary blood flow mainly by a direct effect on splanchnic vessels. This portal hypotensive action, however, was slight. Propranolol decreases portal tributary blood flow by the combination, but not the summation, of its beta 1- and beta 2-blocking effects.