Experimental Study of the Molecular Index of Epidermal Growth Factor in Hepatic Development

ABSTRACT

BACKGROUND: Epidermal growth factor (EGF) is a 6Kd polypeptide hormone produced by the glands of the gastrointestinal tract, namely the salivary and Brunner's glands. In fetal and neonatal life, EGF appears to play an important role in the developement of the gastrointestinal tract and the liver. METHODS: EGF and EGFR (EGF receptor), which play important roles in the onset of liver regeneration, were investigated with regard to the proteins and mRNA according to the developmental periods of the livers of prenatal rats (24 female Spraque Dawley rats weighting from 200 to 250g) by using immunohistochemical stains, the solution reverse transcription polymerase chain reaction (RT PCR), and in-situ (IS) RT PCR. RESULTS: 1) On the immunohistochemical stains, the immunoreactivities for EGF started to be observed at an early stage of the developing rat liver. As the developmental stage progressed, the reactivites were observed in embryo tissues containing epithelial cells. The strongest reactivity for EGF was found from the 17th to the 19th day after pregnancy and decreased gradually till full term. The reactivities of EGFR were detected earlier than those of EGF. 2) In solution RT PCR studies, EGF and beta-actin (house keeping gene) were detected in all developmental stages, reached a peak level at the 18th day after pregnancy, and decreased gradually till the final developmental stage. The peak level of EGF beta-actin was about 4 times higher than the lowest level. 3) The expressions of EGF in IS RT PCR were detected mainly on hepatocytes rather than Kupffer cells and endothelial cells. CONCLUSIONS: The EGF expression was observed over the entire time of development for experimental rat livers and is related strongly to growth and developing rate of liver.