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 les s than 1/4 to that in controls; in those with nephrectomy, the increas e is similar to that in controls. Cervical vagotomy in K-loaded intact dogs does not alter (influence) the increase of serum insulin; in tho se with nephrectomy there is a striking increase. In K-loaded intact d ogs cervical vagotomy added to beta receptor blockade has no influence i.e., the response is the same as that to blockade alone; in those wi th nephrectomy, the increase produced by vagotomy is suppressed. Resul ts suggest that in controls with nephrectomy, the insulin secretory re sponse does not involve beta receptors of pancreatic islet B cells owi ng to restraint by efferent impulses in the cervical vagi. Interruptio n of the impulse by vagotomy releases the restraint, with resulting hy peractivity; the accompanying hyperinsulinemia may be the result of su ppression of the hyperactive receptors by beta receptor blockade.