Oral fructose tolerance, gastric emptying and absorption: a compartmental model

Gastric emptying and intestinal absorption regulate transfer of ingested fructose from stomach to plasma. Using conscious rhesus monkeys we have developed a compartmental model which describes this system. Fructose tolerance tests were performed in groups of monkeys by intragastrically administering 2 g/kg of 10.5% D-fructose solution; fructose concentration in arterial plasma, [fructose], and intragastric volume were measured at intervals afterward. One group was pretreated with atropine; stomachs imptied with a time constant, tau, of 67 min. Another group received fructose solution with trisodium citrate added; tau was 18 min. Another group received only fructose; tau was 30 min. Using these constants, a model was developed to describe the [fructose] data. In this model k1 related amount of fructose in intestine to absorption rate and Ae represented absorption efficiency. K1 = 0.03 and Ae = 89% provided a good fit for data from the atropinized group. k1 = 0.018 and Ae = 56% provided a good fit for data from the other groups. Differences were explained by considering effects of atropine on gastrointestinal secretion. The model adequately describes our [fructose] data and may be adapted for tests utilizing other substances.