[Effects of various oxygen concentrations on metabolic performance of in vitro perfused human placentas]

The aim of the experiments was the in vitro-investigation of metabolic reactions of human placentae under different oxygen supply, particularly when oxygenation followed a period of hypoxia. A perfusion system was used with both circuits of a whole placenta being recirculated over 2 hours with blood-containing perfusate. In group A 17 placentae were perfused under normoxic conditions; in group B 10 perfusions were carried out under hypoxia. In group C 8 placentae were oxygenated after 60 minutes of hypoxic perfusion. (All results are given in mumol/g wet weight/h). In group B glucose uptake (2.95 +/- 1.11) was slightly increased compared to group A (2.59 +/- 1.68), while lactate production was markedly higher (7.69 +/- 1.04 versus 3.56 +/- 1.53 in group A). Oxygen consumption was smaller under hypoxia. Pyruvate showed no significant changes over the 2 hours in all groups. In group C the results of the first hour resembled those of group B. After reoxygenation these placentae showed a smaller oxygen consumption compared to group A, but the highest glucose uptake (4.35 +/- 0.72), whereas lactate production (5.26 +/- 1.86) was lowered compared to group B. The smaller oxygen consumption could be explained by a deterioration of mitochondriae and hence a decreased capacity of oxydative metabolism. The higher glucose uptake could reflect the ability of placental tissue to restore other energy-sources (e.g. proteins) which were affected under the previous hypoxia. Further investigations are required to answer questions of placental function and its disturbances.