Gastrointestinal stability and absorption of insulin in suckling pigs.
Stability and absorption of orally administered fluorescein-isothiocyanate labeled insulin (FITC-insulin) in the gastrointestinal (GI) tract were investigated in newborn and 3-day-old pigs. The uptake of FITC-insulin by the intestinal epithelial cells was visualized using confocal laser scanning microscopy. Following oral administration, 3 h later 56 and 88% of orally administered fluorescence was found in the GI tract in newborn and 3-day-old piglets, respectively. Chromatographic analysis revealed that 15-37% of fluorescence recovered from the gastric and proximal intestinal contents was eluted in the void volume of a Sephadex G-25 column. It was also observed that oral administration of FITC-insulin at a dose of 100 nmol/kg body weight led to a significant decrease in blood glucose in newborn pigs (P<0. 05) but not in 3-day-old pigs. Microscopic examination showed that FITC-insulin was taken up via the vesicular transport mechanism throughout the whole small intestine but the ileum appeared to be a preferred site for FITC-insulin transport in newborn pigs. In 3-day-old pigs, the uptake of FITC-insulin occurred only in the distal part of the small intestine. These findings suggest that milk-borne insulin may partially survive in the GI lumen and subsequently act on the gastrointestinal tract in suckling piglets, while GI absorption of milk-borne insulin is limited to newborn pigs.
Shen
W H
WH
Department of Zoology, The University of Hong Kong, Pokfulam Road, Hong Kong. wshen@iupui.edu
Xu
R J
RJ
D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D001786:Blood Glucose / Q000032:analysis; D004064:Digestive System / Q000378:metabolism*; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives* / Q000378:metabolism; D007328:Insulin / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D018613:Microscopy, Confocal; D013552:Swine
D001786:Blood Glucose; D007328:Insulin; C031573:insulin, fluorescein-isothiocyanated-; D016650:Fluorescein-5-isothiocyanate