The vasodilator actions of isoprenaline, histamine, prostaglandin E2, glucagon and secretin on the hepatic arterial vascular bed of the dog.

The sympathetically-innervated arterial vascular bed of the dog's liver was perfused from a femoral artery. Arterial blood flow and perfusion pressure were measured continuously, and the hepatic arterial vascular resistance calculated. The preparation provided a means of assessing hepatic arterial vasodilatation quantitatively. 2 Isoprenaline, histamine, prostaglandin E2, glucagon and secretin were injected intra-arterially and all evoked dose-dependent vasodilatation of the hepatic arterial vascular bed. 3 The maximum reduction in the calculated hepatic arterial vascular resistance of 37-38% was the same for each of the five substances. 4 Comparisons on a weight basis revealed that prostaglandin E2 was the most potent, followed in potency order by secretin, isoprenaline, histamine and glucagon. 5 Comparisons on a molar basis showed that secretin and prostaglandin E3 were intrinsically considerably more potent than isoprenaline, histamine or glucagon. 6 The onset of the vasodilatator responses to secretin, isoprenaline, histamine and prostaglandin E2, was rapid, and the duration of their actions was brief. 7 The onset of the vasodilator effects of glucagon was slow and its duration of action very prolonged. 8 The implications of these observations with respect to the physiological control of the hepatic arterial vascular bed of the dog are discussed.