GASTROINTESTINAL ABSORPTION OF INSULIN-LIKE GROWTH-FACTOR-I IN NEONATAL PIGS

To determine if milk-borne insulinlike growth factor-I (IGF-I) is abso rbed in neonatal piglets, recombinant human IGF-I was iodinated and th en administered via an oral-gastric tube to newborn and 3-day-old pigl ets together with fluorescent isothiocyanate dextran (FITC-D70s. a mac romolecular marker for assessment of gut closure). Results showed that total radioactivity and trichloroacetic acid (TCA)-precipitable radio activity rose significantly in the plasma of both newborn and 3-day-ol d piglets 1 hour after oral-gastric administration of I-125-IGF-I, alt hough the magnitude of increase was greater in newborns than in 3-day- old piglets. In contrast, significant absorption of FITC-D70s was obse rved only in newborn piglets but not in 3-day-old piglets. Chromatogra phic analysis revealed that I-125-IGF-I represented up to 20% of total plasma radioactivity in the newborns and up to 10% in the 3-day-old p iglets. The I-125-IGF-I found in the plasma was mostly bound to IGF-bi nding proteins. These results indicate that milk-borne IGF-I can be ab sorbed in neonatal piglets and the absorption is independent of gut cl osure.