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Iron metabolism during pregnancy is biased toward maintaining the fetal supply, even at the cost of anemia in the mother. The mechanisms regulating this are not well understood. Here, we examine iron deficiency and supplementation on the hierarchy of iron supply and the gene expression of proteins that regulate iron metabolism in the rat. Dams were fed iron-deficient diets for 4 wk, mated, and either continued on the deficient diet or an iron-supplemented diet during either the first half or the second half of their pregnancy. A control group was maintained on normal iron throughout. They were killed at 0.5, 12.5, or 21.5 days of gestation, and tissues and blood samples were collected. Deficiency and supplementation had differential effects on maternal and fetal hematocrit and liver iron levels. From early in pregnancy, a hierarchy of iron supply is established benefiting the fetus to the detriment of the mother. Transferrin receptor, transferrin receptor 2, and hepcidin mRNA expression were regulated by both iron deficiency and supplementation. Expression patterns showed both organ and supplementation protocol dependence. Further analysis indicated that iron levels in the fetal, and not maternal, liver regulate the expression of liver transferrin receptor and hepcidin expression in the mother. placenta; deficiency; supplementation

BeWo cells are a placental cell line that has been widely used as an in vitro model for the placenta. The b30 subclone of these cells can be grown on permeable membranes in bicameral chambers to form confluent cell layers, enabling rates of both nutrient uptake into the cells from the apical surface and efflux from the basolateral membrane to be determined. The aim of this study was to evaluate structural and functional properties of confluent b30 BeWo cell layers grown in bicameral chambers, focusing on the potential application for studying receptor-mediated uptake and transport of transferrin (Tf)-bound iron (Fe-Tf). While it proved extremely difficult to establish and maintain an intact BeWo cell monolayer, it was possible to grow the cells to a confluent multilayer. Iron, applied as Fe-Tf, was rapidly transported across this cell layer; 9.3 [+ or -] 0.5% of the total dose was transported after 8 h, equivalent to 38.8 [+ or -] 2.1 pmol x [cm.sup.-2] x [h.sup.-1]. Transfer of Tf across the cell layer was much more limited; 2.4 [+ or -] 0.2% of the total dose was transported after 8 h, equivalent to 5.0 [+ or -] 0.4 pmol x [cm.sup.-2] x [h.sup.-1]. Compartmental modeling of these data suggested that iron was transported across the cell layer predominantly, if not exclusively, via a transcellular route, whereas Tf taken up into the cells was predominantly recycled back to the apical compartment. The results suggest that these cells are very efficient at transporting iron and, under carefully controlled conditions, can be a valuable tool for the study of iron transport in the placenta. placenta; fetus; mineral metabolism

Y receptors couple to G proteins and either mobilize intracellular [Ca.sup.2+] or alter cAMP levels to modulate the activity of [Ca.sup.2+]- and cAMPsensitive ion channels. We hypothesize that increased ion transport into the lumen of MDCK cysts can osmotically drive fluid movement and increase cyst size. Furthermore, activation of the adenylate cyclase/cAMP pathway may trigger cell proliferation via an extracellular signal-related kinase cascade. To test this hypothesis, several P2Y receptor inhibitors were used on the MDCK in vitro model of renal cyst formation. The nonspecific P2 receptor inhibitors reactive blue 2 and suramin reduced cyst growth significantly, as did PPADS and, to a lesser extent, the [P2Y.sub.1]-specific antagonist MRS2179. Cyst growth was reduced by ~50% when ATP was removed from the culture medium with apyrase, although stable analogs of ATP failed to increase cyst size. The nonselective P2X receptor inhibitor Coomassie brilliant blue G was ineffective at reducing cyst growth, suggesting no involvement of P2X receptors. Finally, the presence of selective inhibitors of ERK activation (either PD98059 or U0126) greatly reduced cyst growth, whereas in untreated cysts ERK activity was observed to increase with time. We conclude that stimulation of endogenous P2Y receptors by extracellular ATP increases growth of MDCK cysts via cAMP-dependent activation of the ERK pathway. P2Y receptor antagonists may have therapeutic potential in reducing cyst size and slowing disease progression; although further studies in vitro and in vivo are needed to investigate the specificity and role of these P2Y receptors in renal cystic diseases. ATP; polycystic kidney disease; Madin-Darby canine kidney; extracellular signal related kinase; renal cyst growth; ADPKD