Effects of epidermal growth factor on total cellular RNA, protein and leucine aminopeptidase in human colon adenocarcinoma (Caco-2) cells

Both in vivo and in vitro studies have showed that epidermal growth factor (EGF) in human milk could modulate growth and development of fetal intestinal cells. The purpose of this study was to investigate the effect of EGF on growth and the protein digestion enzyme -leucine aminopeptidase (LAP) in human colon adenocarcinoma (Caco-2) cells. The total cellular RNA and protein, and the activity and content of LAP were examined after the addition of EGF at 0, 5 (close to EGF concentration in human milk), 50 (close to EGF concentration in colostrum) or 250 nM. After incubation with EGF 24 h, the total cellular RNA in the EGF treatment groups was elevated to 1.6- to 3.1- fold of the control group as the concentrations of EGF were increased. The 250 nM EGF treatment group had significantly higher total cellular RNA as compared to the control and 5 nM EGF treatment groups. The 5 nM EGF treatment group had higher total cellular protein than the control and 250 nM EGF treatment groups. The LAP specific activity in the EGF treatment groups was 78 ~ 86% of the control group. In addition, LAP (53 kDa) content in the EGF treatment groups was 86 ~ 93% of the control group after separation by 10% SDS-PAGE and analysis by Western blotting. In conclusion, 250 nM EGF treatment increased total cellular RNA and 5 nM EGF treatment increased total cellular protein; however, EGF treatments (5 to 250 nM) had no remarkable effects on the specific activity and content of LAP on the cell membranes of Caco-2 cells.