Glucose responsiveness and acetylcholine sensitivity of pancreatic beta-cells after vagotomy

Abstract

The chronic effects of removal of parasympathetic neural input to the pancreas on in vitro insulin secretion were assessed. Groups of Wistar and Long-Evans rats received total subdiaphragmatic vagotomy or sham operation. Four to ten weeks later, after the return of food intake and body weight in the vagotomized groups to values similar to the sham-operated groups, pancreatic islets were isolated and statically incubated with selected concentrations of glucose and acetylcholine. Two experimental protocols were used. In the first experiment, insulin secretion in response to basal (5 mM) glucose was 59 +/- 15 (SE) and 65 +/- 13% greater in islets from the vagotomized Wistar and Long-Evans groups, respectively, than in the corresponding sham groups. The enhancement of insulin secretion by several doses of acetylcholine observed in islets from sham-operated groups was totally absent in islets from both vagotomized strains. In the second experiment, insulin secretion was determined in response to selected glucose concentrations by using islets from Wistar rats. An upward and leftward shift of the dose-response curve was observed in the vagotomized group causing 5 mM to become a stimulatory glucose concentration and increasing the stimulatory potency of 10 mM glucose. These results suggest that interruption of vagal input to pancreatic beta-cells may induce a compensatory increase in responsiveness to glucose and a functional suppression of acetylcholine receptors. These data provide further support for the hypothesis that vagal input plays a functionally important role in the control of insulin secretion and maintenance of acetylcholine sensitivity.