Epidermal growth factor in mouse milk during early lactation: lack of dependency on submandibular glands

Using a specific and sensitive radioimmunoassay, we found epidermal growth factor (EGF) in mouse milk during early lactation in normal and sialoadenectomized mice. Levels of EGF peaked around the 6th day postpartum and decreased thereafter up to day 12. Sephadex G-50 column chromatography of milk from normal and sialoadenectomized mice showed a single immunoreactive component comigrating with purified 6045 dalton EGF from the mouse submandibular gland. The concentrations of EGF were similar in milk collected from the breast and the stomach of the offspring immediately after feeding. The molecular profiles, concentrations, and ontogeny of EGF in milk of control and sialoadenectomized mice were also similar, suggesting that the submandibular gland is not the major source of EGF in mouse breast milk.