Removal of circulating gastrin and cholecystokinin into the lumen of the small intestine.

This study was undertaken to investigate the mechanism by which the small intestine removes circulating gastrin and cholecystokinin (CCK). A 100-cm (acute study, 10 dogs) or a 50-cm (chronic study, 5 dogs) segment of midjejunum was excluded in all 15 dogs. The excluded loop was perfused with 0.1 M phosphate buffer (pH 7.4), which was constantly recirculated by a peristaltic pump. It the acute control study (5 dogs), gastrin concentrations in the intestinal perfusate were increased gradually to a level of 320 +/- 49 pg/ml at 90 min (i.e., 7.6 +/- 0.9 times higher than serum gastrin levels). In the antrectomy group (5 dogs), perfusate gastrin concentrations were greatly decreased after antrectomy, in consonance with the decrease in serum gastrin concentrations. In the chronic study (5 dogs), perfusate gastrin concentrations were significantly increased after food stimulation, in consonance with the increase in serum gastrin concentrations. CCK was also released into the bowel lumen in considerable amounts basally and after endogenous release. Although one cannot exclude the possibility that a considerable amount of gastrin or CCK in the lumen may originate from the bowel segment, this study shows that the small bowel removes gastrin and CCK from the circulation by their secretion into the bowel lumen. Loss of this mechanism might partially explain the rise in gastrin levels that is observed in some patients after extensive small bowel resections.