The effect of propranolol on the hyperaemic response of the hepatic artery to portal venous occlusion in the dog.

1. It has been reported that activation of beta-adrenoceptors may be responsible for the hyperaemic response of the hepatic artery to portal venous blood flow reduction. 2. The effect of beta-adrenoceptor blockade on the hepatic arterial response to portal vein occlusion was investigated in 6 anaesthetized dogs. A side-to-side portacaval shunt was established to prevent loss of venous return and arterial blood pressure during periods of portal occlusion. Measurements of hepatic arterial and portal venous blood flows were made by use of electromagnetic flow probes. 3. Intravenous propranolol injection, at a dose sufficient to block the vasodilator effect of low doses of exogenous adrenaline, did not alter the magnitude of the hyperaemic response of the hepatic artery. Propranolol also produced no change in baseline portal venous pressure. 4. It is concluded that hepatic beta-adrenoceptors are unlikely to be involved in the arterial response to portal occlusion. The absence of any reduction in basal portal venous pressure by propranolol is of interest in view of the current application of the drug in the treatment of patients with portal hypertension.