Preabsorptive intestinal satiety controls of food intake in pigs.

Pigs, 1--3 mo of age, weighing 5--80 kg, were fitted with duodenal, intraportal, or intrajugular catheters. After a 4-h fast, preloads were delivered to the duodenum, and food intake then measured for 10 min (no drinking water). Glucose (5--40%) and NaCl (0.9--6.5%) solutions were used as preloads (5 ml/kg body wt). Food intake expressed as percent control intake (Y) was depressed in proportion to preload concentration (X): for glucose, Y = 109 - 2X; for NaCl, Y = 107 - 13X. When expressed in osmoconcentration, glucose and NaCl preloads had nearly identical satiety effects. Preloads of 40% sorbitol depressed intake to 74% control. Intrathoracic vagotomy reduced the satiety effects of glucose and NaCl solutions by 50%. Tetracaine (0.5%) in the hypertonic preloads blocked 80% of the satiety effects of the glucose and NaCl preloads, but had no effect on sorbitol satiety effect. Injection of glucose or NaCl solutions into the portal or jugular veins had no significant effect. It was concluded that duodenal osmoconcentration to the degree that it exceeds body fluid tonicity contributes to the immediate satiety seen during a meal.