CHEMICAL SPECIFICITIES AND INTESTINAL DISTRIBUTIONS OF NUTRIENT-DRIVEN SATIETY

We measured intakes of sham- and naturally feeding rats during gut per fusions of nutrients. Our objectives were to determine 1) which nutrie nt products in gut lumen suppressed intakes; 2) how suppression by var ious nutrients is distributed along gut; and 3) whether time courses o f suppression were similar among different nutrients. We found that sa tiating nutrients consisted of fatty acids only longer than 10 carbons , of monomeric carbohydrates only with affinity for the glucose transp orter, and, among several amino acids, of only phenylalanine and trypt ophan. Dimeric maltose had about the same potency as an isocaloric mix ture of longer glucose polymers; since responses to either were blocke d by a glucosidase inhibitor, each probably acted after hydrolysis to free glucose. Effective nutrients suppressed intakes about equally on infusion into duodenum vs, midgut, and the same nutrients also suppres sed intakes when infused into colon. Food intakes were suppressed only while maltose was infused, not after it was stopped, but suppression persisted for 2 h after stopping perfusions with fatty or amino acids.