The effect of portal and jugular infused glucose, mannitol and saline on food intake in dogs

Abstract

Hepatic glucoreceptors have been hypothesized to have an important role in determining normal hunger and satiety. In the present study 23 dogs were fitted with chronic hepatic portal and jugular vein cannulas. The dogs were fed for 1 hr/day. On infusion days (total of 318 infusions) the animals were infused into the portal or jugular veins with a 30% glucose solution (2.4 or 3.6 g/kg, b.wt.), 0.9% NaCl as a volume control or 30% mannitol as an osmotic control and then fed 10 minutes later. The data showed that the dog's food consumption was similar after they received glucose or the appropriate control infusion regardless of the infusion site. Some dogs had blood samples taken for glucose and insulin determinations prior to infusion, at the middle and end of infusion, just prior to food presentation and at the end of the feeding period. Saline and mannitol infusions did not alter plasma glucose or insulin concentrations; whereas there were marked increases in plasma glucose (6–8 x) and insulin (18–19 x) following glucose infusions. Postinfusions glucose values indicated approximately 72% of the infused dose glucose (∼43 g) had left the plasma prior to food presentation. Despite the large increases in plasma glucose and insulin, as well as glucose storage and/or oxidation, the dogs consumed amounts of food similar to that eaten after control infusions. Similarly, prefeeding the dogs 20% of their average daily intake prior to infusion did not alter the animals subsequent intake. These data are in agreement with earlier work from our laboratory and question the role of the hypothesized hepatic glucose satiety receptors.