EFFECTS OF LACTOFERRIN AND ITS PEPTIDES ON PROLIFERATION OF RAT INTESTINAL EPITHELIAL-CELL LINE, IEC-18, IN THE PRESENCE OF EPIDERMAL GROWTH-FACTOR

The cell growth-stimulating activity of lactoferrin (LF) in combinatio n with epidermal growth factor (EGF),vas evaluated by using a rat inte stinal epithelial cell line, IEC-18. LF was found to be more effective than EGF for inducing an increase in cell numbers when cultured for o ver 6 days using a medium containing 0.2% fetal calf serum (FCS), alth ough the H-3-thymidine incorporation-stimulating activity of EGF was m ore potent than that of LF, A synergistic effect of LF and EGF was obs erved in both cell proliferation and DNA synthesis assays, The increas e in cell numbers when stimulated with LF plus EGF corresponded to abo ut 5 times that of the control, Tron was not required for manifestatio n of these effects of LF, On the other hand, iron-saturated transferri n (TF) had cell-growth-stimulating activity, but iron-free TF did not, either in the presence or absence of EGF, These results indicate that LF induces cell proliferation by a mechanism distinct from that of TF , A pepsin-generated hydrolysate of LF (LFH) had an activity similar t o that of undigested LF, and a peptide with cell-growth-stimulating ac tivity from bovine LFH was isolated by monitoring its effects in combi nation with EGF on DNA synthesis in IEC-18 cells, Sequence analysis in dicated that the peptide has the structure e-Tyr-Gly-Thr-Lys-Glu-Ser-P ro-Gln-Thr-His-Tyr-Tyr, corresponding to residues 79-93 of bovine LF.