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THE VASODILATOR ACTIONS OF ISOPRENALINE, HISTAMINE, PROSTAGLANDIN E2, GLUCAGON AND SECRETIN ON THE HEPATIC ARTERIAL VASCULAR BED OF THE DOG

1 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 E2 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.