Stimulatory effect of human lactoferrin on DNA synthesis in BALB/c 3T3 cells.

The DNA synthesis-stimulating activity of holo-lactoferrin from human milk was demonstrated using BALB/c 3T3 cells. The stimulatory effect of lactoferrin was caused by the iron bound to the lactoferrin, because the lactoferrin molecule itself did not stimulate the DNA synthesis in the absence of iron. Previously, however, such stimulatory activity of lactoferrin had been thought to be restricted to human cell lines. The maximal degree of DNA synthesis attained in the presence of holo-lactoferrin was found to be about 4-fold greater than that attained in the presence of holo-transferrin. Transferrin had neither a synergistic nor inhibitory effect on the DNA stimulating activity of lactoferrin. From these results and the fact that the iron-binding affinity of lactoferrin is higher than that of transferrin, especially at low pH values, it is possible that the mechanism of iron-transportation is different between lactoferrin and transferrin. Lactoferrin from bovine milk was as effective as human lactoferrin.