The distribution and characterization of 59Fe in the maternal liver, maternal blood, placenta, and fetal liver were examined in rats of late gestation 3 and 24 hours after intravenous 59Fe-iron administration. The following results were obtained bythe comparison of 59Fe incorporation 3 and 24 hours later.
1) The incorporation into the maternal liver was reduced from 29.5% to 14.1%, that into maternal blood was increased from 5% to 12%, that into placenta was increased from 3.3% to 7.4%, and that into fetal liver was increased from 9.3% to 13.4%, respectively. But the change of 59Fe incorporation into the liver and blood in non-pregnant rats at these intervals was not so strong, when compared with pregnant rats.
2) The identification of 59Fe-containing compounds from the livers and placenta was achieved by gel-filtration on Sephadex G-75 and qualitative immunoreactions. On the maternal liver, 59Fe was mainly incorporated into ferritin and transferrin fractions, but on the placenta and fetal liver, a considerable amount of 59Fe was recognized in the small molecular (M. W. 18, 000) and rather heat labile protein, in addition to those of the already detected proteins.
3) The distribution of 59Fe incorporated into isoferritins of the livers and placenta was investigated by ampholyte-gel isoelectric focusing. 59Fe was largely incorporated into rather acidic isoferritins 3 hours after the injection, but the incorporation was shifted to basic isoferritin after 24 hours. However, protein detections showed no significant difference in the livers and placenta either 3 or 24 hours after the injection, compared with those of the control.
