Stimulation of Insulin Secretion by Parasympathomimetic Agents

Abstract

Effects on insulin secretion of methacholine and bethanechol given systemically and infused into the pancreatic artery were studied in the anesthetized dog. An intramuscular injection of methacholine (0.2 mg/k) resulted in a striking elevation of plasma immunoreactive insulin (IRI) in both pancreatic vein and femoral artery. A rapid intravenous injection of bethanechol (0.05 mg/k) caused a prompt and less prominent increase in pancreatic venous plasma IRI, and a somewhat delayed elevation in femoral artery plasma IRI. A constant infusion of bethanechol (1 μg/k/min) into the pancreatic artery also induced an abrupt and significant rise in pancreatic vein plasma IRI and a delayed augmentation in femoral artery plasma IRI. The increase in plasma IRI in the pancreatic and femoral vessels upon a similar local infusion of methacholine (1 μg/k/mvn) was more conspicuous than on bethanechol infusion. The elevation in plasma IRI by a local infusion of both cholinergic agents was totally blocked by a preceding infusion of atropine (0.0015 mg/k/min for 15 min), which did not prevent plasma IRI from increasing prominently following local infusion of glucose. A significant increase in the blood sugar level was observed after administration of the parasympathomimetic agents. The rise in pancreatic vein plasma IRI appeared clearly before the occurrence of hyperglycemia after systemic intravenous injection or local infusion of the agents. (Endocrinology83: 651, 1968)