Insulin-like growth factor-I affects amino compounds in the fluids of the chicken embryo

The concentration differences of more than 40 amino acids and related compo unds in the amniotic fluid, allantoic fluid, and plasma of the chicken embr yo are maintained by specific barriers. Since the amniotic and allantoic me mbranes are not innervated, we proposed that these barriers are controlled by hormones. Specific effects of insulin and prolactin on the amino compoun ds in the three fluids confirmed this hypothesis and raised the question of the possible role of growth factors. Application of insulin-like growth fa ctor-1 (IGF-I) to the chorioallantoic membrane of day 13 chicken embryos ca used the following concentration changes in 41 amino compounds measured 1 a nd 2 h later: (1) in the amniotic fluid, an increase of 40 compounds, regar dless of the presence or absence of a concomitant stress effect on these co mpounds; only NH3 was not affected; (2) in the allantoic fluid, a decrease of reduced glutathione (GSH) and anserine, and an increase of NH3; (3) in t he plasma, a decrease of 24 compounds. Within the same time frame, stress c aused in the amniotic fluid a drop of the concentration of 29, and an incre ase of 5, amino compounds; IGF-I reversed the stress effect on all 29 compo unds the concentrations of which had dropped and enhanced the stress-induce d increase of the other 5 compounds. In the allantoic fluid, stress induced an increase of GSH; IGF-I reversed this effect. In the plasma, stress caus ed an increase of 9 compounds; IGF-I counteracted the increase in 7 cases. These findings indicate new and unexpected roles of IGF-I in the prenatal r egulation of amino compounds. (C) 2001 Academic Press.