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Adenine Nucleotide Catabolism in the Human Trophoblast Early and Late in Gestation

ABSTRACT: Trophoblastic cells were separated and cultured from human first trimester and term placentae for studies on energy metabolism. Changes in the catabolism of prelabeled adenine nucleotides and the adenylate energy charge (EC) were followed during energy deprivation. EC was 0.70 ± 0.04 (mean ± SD) in the first trimester and 0.65 ± 0.08 in the term cells before experiments. Both during hypoxia (N2-atmosphere) and in the absence of glucose, ATP and EC were preserved for up to 8 h. 2-Deoxyglucose caused a fall in ATP to 12.1 ± 5.0 and 14.8 ± 7.4% of initial levels, and in EC to 0.46 ± 0.04 and 0.42 ± 0.05 in the first trimester and term cells, respectively. In first trimester cells, inhibition of oxidative phosphorylation by rotenone in the absence of glucose resulted in a significantly slower reduction of ATP and EC than after deoxyglucose, whereas in term cells, the initial responses were similar. Of total adenine nucleotides degraded, 7.1–10.5% were released extracellularly as adenosine, when its deamination was inhibited. Human trophoblast appears to tolerate transient hypoxia or deprivation of exogenous glucose. Susceptibility to energy deprivation increases with gestational age. The main pathway for AMP-catabolism is deamination, but the trophoblast is able to produce adenosine during accelerated adenine nucleotide catabolism.