1 The somatostatin octapeptide-analogue, octreotide, is absorbed as in
tact peptide from the gastrointestinal (GI) tract. 2 In situ absorptio
n experiments in rats confirmed our recent intubation studies in human
volunteers demonstrating that the peptide has preferential absorption
sites in the small intestine. Absorption of octreotide was higher in
the jejunum than in the duodenum or the ileum. 3 Experiments with bile
-duct cannulated rats demonstrated that the absorption of octreotide d
ecreased in the presence of bile, reflecting a negative influence of b
iliary components on the absorption of the peptide. 4 Uptake experimen
ts using rat jejunal brush border membranes were performed to analyse
the absorption mechanisms. The transport of octreotide into jejunal br
ush border membranes was significantly higher than the uptake into mem
brane vesicles isolated from rat ileum. When initial uptake (0-15 s) r
ates into the membrane vesicles were calculated as a function of the p
eptide concentration, a saturable component could be observed, indicat
ive of transport mechanisms different from simple diffusion.