Effects of catecholamines and their inhibitors on the isolated canine pancreas. I. Noradrenaline and isoprenaline

Abstract

alpha Adrenergic agonist (noradrenaline, 2, 20, and 200 mug) and antagonist (phenoxybenzamine, 15 mg), and beta adrenergic agonist (isoproterenol, 2, 20, and 200 mug), and antagonist (propranolol, 6 mg), were tested on isolated perfused canine pancreas under basal conditions, and under stimulation by a background of secretin (0.5 clinical unit per hr), or of caerulein (600 to 1200 ng per hr). Noradrenaline induced a strong vasoconstriction (inhibited by phenoxybenzamine), followed by a moderate vasodilation (possibly mechanical). Noradrenaline did not stimulate a resting pancreas and inhibited a pancreas from secreting in response to secretin or caerulein. After phenoxybenzamine, in the absence of vasoconstriction, this latter effect was reversed into a dose-dependent stimulation of hydrelatic secretion, suggesting that noradrenaline had a direct action on the secretory cell. There was no stimulation of protein and no acinar degranulation. Propranolol and atropine did not modify the effectiveness of noradrenaline. Isoprenaline had a weak vasodilatory effect but no effect on the secretion. Adrenergic blocking agents did not alter the response to secretin or caerulein.