Epidermal growth factor in human and bovine milk.

The concentration of epidermal growth factor in human and bovine milk was measured by radioreceptor assay. Both human placental plasma membranes and a human epidermoid carcinoma cell were used as the epidermal growth factor receptor source in the assay. The use of placental plasma membrane in the radioreceptor assay gave erroneous results for bovine milk and overestimated the concentration of epidermal growth factor in human milk. Intact cells appear to provide a more accurate measure of the concentration of epidermal growth factor in milk samples. Using A431 cells, we found very low concentrations of epidermal growth factor in bovine milk (less than 2 ng/ml) compared to human milk (30-40 ng/ml). No epidermal growth factor activity was found in several cows' milk-based infant formulas. These results highlight the caution which must be taken when measuring trace substances such as polypeptide growth factors in complex samples such as milk.