Vagal modulation of the insulin secretory response to KCl loading in nephrectomized dogs

In K-loaded intact and nephrectomized control dogs there is a four-to five-fold increase of basal serum insulin. With beta receptor blockade in K-loaded intact animals the increase of basal serum insulin is less than 1/4 to that in controls; in those with nephrectomy, the increase is similar to that in controls. Cervical vagotomy in K-loaded intact dogs does not alter (influence) the increase of serum insulin; in those with nephrectomy there is a striking increase. In K-loaded intact dogs cervical vagotomy added to beta receptor blockade has no influence i.e., the response is the same as that to blockade alone; in those with nephrectomy, the increase produced by vagotomy is suppressed. Results suggest that in controls with nephrectomy, the insulin secretory response does not involve beta receptors of pancreatic islet B cells owing to restraint by efferent impulses in the cervical vagi. Interruption of the impulse by vagotomy releases the restraint, with resulting hyperactivity; the accompanying hyperinsulinemia may be the result of suppression of the hyperactive receptors by beta receptor blockade.