FATE OF OROGASTRICALLY ADMINISTERED INSULIN-LIKE GROWTH FACTORS I AND II (IGF-I AND -II) TO SUCKLING RATS

Abstract

IGF's are stimulators of mitosis and may be of importance in the regulation of intestinal growth in the neonate. Since IGF's are present in a variety of milks, we tested the hypothesis that ingested milk-borne IGF's might be available to gastrointestinal (GI) tissues and might also be absorbed to sites distant to the GI tract. Recombinant 125I-IGF-I and -II in rat milk were given via stomach tube to suckling rats. Approximately 40% of IGF-I or-II cpm remained in the GI tract at 30 min post ingestion with < 1 % appearing in most other organs. Gel chromatography demonstrated that much of radioactivity present in GI tract homogenates eluted together with authentic IGF. Significant differences we re noted in amounts of IGF-I vs-II found in GI tissues after 30 min, particularly in stomach and intestinal wall and lumen. Exogenous IGF-I represented twice the amount of IGF-II in these tissues. Competitive binding studies confirmed that binding of radioactivity present in peaks at 7.5K MW were identical to those of native 125I-IGF's. These studies show that milk-borne IGF remains intact in the GI tract of suckling rats for at least 30 min post ingestion.