Competition of Mn2+ and Zn2+ with 59Fe2+ and 59Fe3+ for the plasma membrane receptors from lactating mouse mammary gland.

Nonlabeled MnCl2 and ZnSO4 compete with 59Fe(2+)-ascorbate and 59Fe2(3+)O3 for transport binding sites situated on the plasma membranes of lactating mouse mammary gland cells. The binding was found to be a process reaching saturation. The heterologous competition used here ruled out the participation of transferrin and to propose that Fe, Mn, and Zn are transported from blood to milk by a mechanism involving one receptor during lactation. Further experiments are necessary to establish the details of the transport mechanism.