EFFECT OF EPIDERMAL GROWTH-FACTOR ON PLACENTAL AMINO-ACID-TRANSPORT AND REGULATION OF EPIDERMAL GROWTH-FACTOR RECEPTOR EXPRESSION OF HEPATOCYTE IN RAT

We investigated the effect of epidermal growth factor (EGF) on amino a cid transport in the rat placenta and the hormonal and nutritional reg ulation of hepatic expression of epidermal growth factor receptor (EGF R). Fetuses horn to maternal rats administered EGF were larger than co ntrol fetuses, while fetuses born to mothers administered EGF antibody were smaller than controls. The fetomaternal amino acid concentration ratio (fetal blood/maternal blood) was higher in the EGF-treated grou p than in the control group, and was lower in the EGF antibody-treated group. EGF treatment stimulated C-14-aminoisobutyric acid, isoleucine and alanine uptake by placental explants as did treatment with insuli n-like growth factor-I and insulin, which have been reported to stimul ate the active amino acid transport. Thus, EGF promoted amino acid tra nsport in the rat placenta and influenced fetal growth as a result. In addition, retinol induced a 170% increase of EGF binding to rat hepat ocytes and insulin induced a 120% increase of EGF binding, while amino acids (isoleucine and serine) had no effect on EGF binding. This resu lt indicated that there is hormonal regulation of EGF binding to hepat ocytes and that changes of some hormone levels may affect hepatic ECGR expression.