Effect of truncal vagotomy on GIP release induced by intraduodenal glucose or fat in dogs.

In order to elucidate the role of the vagus nerve in the release of gastric inhibitory polypeptide (GIP), mongrel dogs were given a 4-min intraduodenal infusion of 10 g glucose or 5 g soybean oil before and again 1 month after truncal vagotomy (TV). The basal GIP concentrations were significantly elevated after TV. The plasma GIP levels following glucose infusion in the vagotomized dogs were significantly higher than those in the untreated dogs, whereas the GIP levels following fat infusion were not affected by TV. These results suggest that TV influences glucose-induced GIP release but not fat-induced GIP release, indicating that different mechanisms of the vagus nerve may be involved in glucose- and fat-induced GIP secretions.