Effect of Pancreatic Adrenergic Tone Modifications Prior to Glucose-Induced Insulin Secretion

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Abstract
The influence of reserpine-induced catecholamine depletion on insulin secretion elicited by 300 mg% glucose (Gl) was studied. The insulin response to Gl stimulation is lower, during both phases of secretion, in the reserpine-treated rat pancreas (R) than in the normal rat pancreas (N). Concurrent perfusion of 10 and 20 ug/ml reserpine plus Gl does not alter the insulin secretion pattern caused by the latter. The presence of norepinephrine (NA) in the perfusate (15 ng/ml) inhibits both phases of glucose-induced insulin release in the N pancreas. However, when NA is perfused for 30 minutes during the pre-stimulatory period, Gl-induced insulin release by the R pancreas reaches values similar to those found in the N pancreas. If propranolol (P), 0.5 ug/ ml, phentolamine (F), 1 ug/ml, or Imidazole (Im), 250 mg%, is perfused together with NA during the pre-stimulatory period, the Gl-induced insulin response of the R pancreas is again inhibited in both phases. The need for a pre-existing normal adrenergic tone for correct insulin response to glucose is postulated. The alpha and beta components, as well as an appropriate level of 3'5' adenosine monophosphate, seem to be necessary in the mechanism of action of the adrenergic tone prior to pancreatic stimulation by glucose.

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