EXOGENOUS INSULIN-LIKE GROWTH-FACTOR-I INCREASES WEIGHT-GAIN IN INTRAUTERINE GROWTH-RETARDED NEONATAL PIGS

Many cases of intrauterine growth retardation (IUGR) are the result of placental insufficiency, suggesting that potential therapies should f ocus on the neonate rather than the pregnant female. We wished to dete rmine whether IGF-I could be used therapeutically to stimulate normal rates of growth in these neonates. Eight sows received 2.3 kg/d of eit her a control (13% protein) or protein restricted (0.5% protein) diet from d 63 of pregnancy to parturition. Litters were reduced to 6 pigs at 3 d of age, and IUGR neonates were fostered onto a control sow. Thr ee pigs/litter received an osmotic minipump containing either saline o r recombinant human IGF-I, delivered at 4 mu g/h from d 3 to d 10 of a ge. Tissue protein synthesis was measured in all pigs using a flooding dose of [H-3]phenylalanine. At birth, both body weight (10%) and circ ulating IGF-I concentration (30%) were significantly lower in IUGR tha n in control newborns. The infusion of IGF-I to IUGR neonates signific antly increased the circulating concentration of IGF-I, growth rate, a nd protein and fat accretion to control levels. The infusion of IGF-I did not alter concentrations of insulin, glucose, IGF-II, or the thyro id hormones. Our results suggest that IGF-I may be a potential therapy to restore normal growth in IUGR infants.