Response of rat mammary gland transferrin receptors to maternal dietary iron during pregnancy and lactation.

Mammalian milk iron (MFe) concentration decreases during lactation. In human attempts to increase MFe through supplementing the mother with iron during lactation have failed and no correlation between maternal iron status or intake and MFe has been determined, suggesting a regulatory mechanism. In contrast MFe in lactating rats can be affected by very high or low amounts of ingested iron. We previously described a transferrin receptor (TfR) mechanism that controls iron entry into rat mammary tissue. In this study lactating rats were used to determine effects of varying dietary iron during gestation and lactation on mammary TfR and MFe. Dams fed low-iron diets had a small increase in TfR, lower hematological indices (p less than 0.005), and lower MFe (p less than 0.005) than did controls or dams fed high iron. Dams fed the high-iron diet had a significant increase in TfR without a concomitant increase in MFe. There was no correlation between MFe and TfR. These findings suggest that control of MFe lies after iron entry into mammary tissue.