The metabolism of the isolated artificially perfused guinea pig placenta. II. Difference of excretion of hydrogen ions, ammonia, carbon dioxide and lactate into maternal and fetal veins.

The isolated and artificially perfused guinea pig placenta produces hydrogen ions, ammonia, lactate and carbon dioxide, which are secreted in significant larger amounts into the maternal than into the fetal circulation. The excretion rates of hydrogen ions, lactate and carbon dioxide increase significantly on both sides when the perfusion flow rates are enhanced. If the maternal perfusion flow is reversed the amount of substances excreted at the maternal side is not different from the amount excreted at the fetal side. A reversal of the fetal perfusion flow does no influence the different excretion rates on the maternal and on the fetal side. This unequal distribution between maternal and fetal side can be explained by the anatomical structure of the placenta. In the interlobium, which has been described as area of metabolism, fetal capillaries are rare. Therefore the metabolites of the placenta itself arrive chiefly at the maternal circulation.