The concentration of serotonin (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in various body fluids was measured during the perinatal period in two groups of infants born with normal and pathological conditions, respectively. Evidence was obtained showing that fetal blood 5-HT level was relatively stable, uninfluenced by maternal or fetal factors, and was about half the value of the maternal blood. High levels of 5-HIAA and evidence of an active decomposition of 5-HT were found in the amniotic fluid. These findings suggest that 5-HT in utero is subjected to a very active metabolic turnover. The origin of the fetal blood 5-HT and the significance of the placenta in the control of intrauterine 5-HT metabolism is discussed. There was no clear evidence of abnormal 5-HT metabolism in toxemic pregnancies, premature babies, and an infant with Down’s syndrome in the perinatal period.

Summary. The transfer of iron from maternal blood to the foetuses was determined from the uptake of Bopg by the foetuses found 24 hours after the intravenous injection of ^OFe-labelled plasma or erythrocytes into pregnant cats in the last one-third of pregnancy. A mean value of 2-7 ng Fe was transferred from maternal plasma, whereas 176 ng was transferred from erythrocytes. It was concluded that the major source of foetal iron in the cat is maternal erythrocytes, and that transfer from maternal plasma is quantitatively insignificant. INTRODUGTION.In animals with the haemochorial type of placenta the rate of iron transfer across the placenta from maternal plasma is sufficient to account for all iron accumulated by the foetus (Vosburgh and Flexner, 1950;Bothwell, Pribilla, Mebust and Finch, 1958;Glasser, Wright and Heyssel, 1968;Fletcher and Suter, 1969;Seal, Sinha and Doe, 1972). Hence, it has been concluded that, in animals with haemochorial placentas, iron is transferred directly from the plasma iron-carrying protein, transferrin, to the placenta and thence to the foetal circulation. By contrast, however, in animals vvith endotheliochorial types of placenta the rate of iron transfer from maternal plasma to foetuses found using plasma transferrin-bound 59pg g^ a tracer was much less than that required for foetal needs (Seal et al, 1972;Baker and Morgan, 1973). This was probably due to the fact that the majority of the iron transferred to the foetuses was derived from a source other than maternal plasma transferrin, most likely maternal erythrocytes; but it may have resulted from delayed transfer of iron across the placenta. These possibilities were investigated in the present experiments performed in the cat which has an endotheliochorial type of placenta. Iron-59 was used as a tracer. It was administered to the pregnant animals in two forms, either bound to plasma transferrin or incorporated into erythrocytes. Iron uptake by the placentas, foetal membranes and foetuses was calculated from the 50Fe found in these tissues 24 h after the injections. MATERIALS AND METHODS.Pregnant cats in the latter one-third of pregnancy were used. The gestation age was estimated from the foetal weight (Goronios, 1933).Plasma transferrin-bound ^^Fe was obtained by incubating freshly obtained cat plasma with ssFeGlg for 1 h, with care that the amount of iron added to the plasma did not exceed 50% of its iron-binding capacity. Erythrocytes labelled with sopg were obtained from nonpregnant donor cats which had been injected intraperitoneally with isotonic 59Fe-ferric citrate 4-7 days prior to bleeding from a radial vein, using heparin as an anticoagulant. The cells were washed twice with cold 0-15M NaGI.