HPLC-UV measurements of metabolites in the supernatant of endothelial cells exposed to oxidative stress.

2,8-Dihydroxyadenine (2,8-DHA) was identified by high-performance liquid chromatography with ultraviolet detection as a major metabolite in the supernatant of endothelial cells of the pulmonary artery (PAECs) and aorta (AECs), in addition to hypoxanthine, xanthine, uric acid, and uracil. Under normoxic, hypoxic, and hyperoxic conditions, the concentrations of all the identified metabolites change with time, marking the response of endothelial cells to stress, as a result of changes in cellular metabolism. Thus, the metabolites can serve as stress markers, and their concentrations can indicate the type and the level of cell stress. The results verify that PAECs adapt to survive oxidative stress of hyperoxia. However, AECs can adapt to hypoxia only for a short time and do not survive prolonged hypoxia. The role of the polyamine synthesis pathway in the formation of the unsalvaged adenine, as a possible source of 2,8-DHA, is discussed.