The role of adenosine in the hyperaemic response of the hepatic artery to portal vein occlusion (the ‘buffer response’)

1 Adenosine has been shown to be responsible for the hyperaemic response of the hepatic artery to portal vein occlusion (the hepatic arterial ‘buffer response’). 2 The effect of adenosine receptor blockade and of adenosine uptake inhibition on the hepatic arterial response to portal vein occlusion was investigated in three groups of anaesthetized dogs. 3 Venous return and arterial blood pressure were maintained during periods of portal occlusion by establishing a side‐to‐side portacaval shunt. Hepatic artery and portal vein blood flows were measured with electromagnetic flowmeters. 4 Hepatic arterial infusions of 8‐phenyltheophylline (500 μg kg−1 min−1) and 3‐isobutyl‐1‐methylxanthine (75 μg kg−1 min−1), doses sufficient to block the vasodilator response of the hepatic artery to exogenously applied adenosine, reduced the magnitude of the ‘buffer response’ by 50% and 75%, respectively. 5 Intravenous infusion of dipyridamole (100 μg kg−1 min−1), a dose sufficient to potentiate the vasodilator response of the hepatic artery to exogenously applied adenosine, had little effect on the ‘buffer response’. 6 It is concluded that adenosine is an important, but not the sole, agent responsible for the hepatic arterial ‘buffer response’.