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