A study of the inhibition of adrenaline-induced vasoconstriction in the isolated perfused liver of rabbit

We have studied the action of a series of vasoactive and antispasmodic agents on the intrahepatic vasoconstriction induced by adrenaline in the isolated perfused liver of rabbits. The arterial and portal venous resistance, oxygen consumption, liver weight and bile flow were investigated. The drugs used were as follows: nonspecific alpha-adrenergic antagonists (DH-ergocristine, dibenamine, phenoxybenzamine), vasodilators with a direct miscellaneous action (theophylline, papaverine, dipyridamole, glucagon, Aiu-cor by Instituto Gentilli, Italy [inosine, ATP, IPI, UTP]) and antispasmodics (piperylone, tropenziline, noraminophenazone). Adrenaline increased arterial and portal venous resistance followed by a diminution of oxygen consumption, liver weight and bile flow. alpha-Adrenergic antagonists inhibited the effects of adrenaline on portal venous resistance and oxygen consumption and especially the effects on hepatic arterial resistance. The most potent agent was phenoxybenzamine. In contrast to alpha-adrenoceptor blockade, the effects of other vasoactive agents were without a sustained influence on hepatic arterial resistance (excepting those of glucagon and dipyridamole). Some of them were effective as antagonists on responses in the portal venous bed (papaverine, Aiu-cor). Moreover, there were drugs exerting an enhancement of the vasoconstrictor responses of hepatic artery to low concentrations of adrenaline with no effect on the portal venous bed (piperylone, tropenziline). Theophylline and noraminophenazone exerted no effect either on the arterial or portal venous bed. No vasodilator agent antagonized the changes of the bile flow after adrenaline administration.