Concentrations of epidermal growth factor in mouse milk throughout lactation

A radioimmunoassay was used to measure the concentration of epidermal growth factor (EGF) in mouse milk throughout lactation. The EGF content of mouse milk increased steadily from birth to a concentration of 427 micrograms/l at day 8 of lactation. These high levels were maintained until the approach of weaning, when values decreased from day 17 to 130 micrograms/l at day 22. Milk samples chromatographed on a Biogel P10 column gave a major peak of immunoreactivity at the point at which pure standard EGF was eluted. The origin of milk EGF is unknown, but the high concentrations of this peptide identified in mouse milk suggest that it must play a role in the neonate.