Susceptibility of placental mitochondria to oxidative stress.

Background: Two different mitochondrial fractions (MFs) have been characterized in the human placenta: the "light" and "heavy" fractions (LMF and HMF). Although these organelles are the main source of reactive oxygen species, an imbalance between their production and the rate of detoxification represents a serious threat to mitochondrial homeostasis and, in the case of the placenta, also to the fetus. The aim of this study was to evaluate the antioxidant capacity and susceptibility to oxidative stress in both types of MFs.

Methods: Human MFs were isolated from healthy donors (n = 11) and either incubated or not with H O . Catalase (CAT) activity, and reduced glutathione (GSH), lipid peroxidation (LP), and protein carbonylation (PC) levels were determined.

Results: H O treatment increased LP and PC levels and decreased CAT activity. GSH levels were similar in control and treated MFs.

Conclusion: H O caused oxidative damage in both LMF and HMF and the antioxidant system measured in these two MFs responded similarly. To the best of our knowledge, this is the first partial description of the antioxidant defense in placental HMF and LMF performed in a cell-free assay. The small number of antioxidant system parameters measured did not allow detecting differences between HMF and LMF.