Iron transporters in rat mammary gland: effects of different stages of lactation and maternal iron status.
BACKGROUND
Mechanisms regulating iron transfer from maternal circulation into milk are yet unknown. Whether intestinal iron transporters, divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1), are present in the mammary gland and are involved in iron transfer into milk are unknown.


OBJECTIVE
The objective was to examine DMT1 and FPN1 in rat mammary gland at different stages of lactation and to evaluate the effects of maternal iron status.


METHODS
Rats were fed either 35 mg Fe (control rats) or 8 mg Fe (low-iron rats) per kg diet for 3 wk and were fed the same diet throughout pregnancy and lactation. Mammary gland DMT1, FPN1, transferrin receptor, and ferritin were examined in control rats on days 1, 5, 10, and 20 of lactation and in low-iron rats on days 10 and 20 of lactation. Tissue and milk iron were measured.


RESULTS
Milk iron, DMT1, and FPN1 decreased throughout lactation. Iron status was compromised in low-iron rats, whereas milk iron was maintained. On day 10 of lactation, mammary gland iron and ferritin were lower in the low-iron rats. DMT1, FPN1, and transferrin receptor values were unchanged; however, a smaller-size DMT1 protein was observed in the low-iron rats. On day 20, transferrin receptor increased in the low-iron rats, whereas mammary gland iron, ferritin, DMT1, and FPN1 were unchanged.


CONCLUSIONS
The results show that DMT1 and FPN1 concentrations are higher during early lactation and are possibly involved in iron transfer into milk. Mammary gland regulation of DMT and FPN1 during low iron status appears to be different from that in the intestine.
Leong
Weng-In
WI
Department of Nutrition, University of California, Davis, CA 95616, USA.
Lönnerdal
Bo
B
D000818:Animals; D000833:Animals, Suckling; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000276:immunology / Q000378:metabolism*; D005260:Female; D005293:Ferritins / Q000378:metabolism; D006454:Hemoglobins / Q000032:analysis; D007150:Immunohistochemistry; D007501:Iron / Q000008:administration & dosage / Q000032:analysis / Q000378:metabolism*; D033862:Iron-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism; D008892:Milk / Q000737:chemistry* / Q000378:metabolism; D023421:Models, Animal; D009752:Nutritional Status; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011990:Receptors, Transferrin / Q000378:metabolism; D013997:Time Factors; D000098742:Ferroportin; D000099236:Solute Carrier Family 11, Member 2
D027682:Cation Transport Proteins; D005293:Ferritins; D006454:Hemoglobins; D007501:Iron; D033862:Iron-Binding Proteins; D011990:Receptors, Transferrin; D000098742:Ferroportin; D000099236:Solute Carrier Family 11, Member 2