THE H2O2 INDUCED EFFECTS ON PURINE METABOLISM IN HUMAN ENDOTHELIAL-CELLS

The effects of hydrogen peroxide (H2O2) on the purine metabolism of hu man endothelial cells were investigated. An incubation with 0.01 mM H2 O2 over 60 min led to an increase in the intracellular adenosine-5-tri phosphate (ATP) and creatine phosphate (CP) levels by 51.3% and 18.2%, respectively. A 60 min incubation with 0.1 mM H2O2 showed no effect. The uptake and salvage of C-14-adenine (C-14-AD) and C-14-adenosine (C -14-ADO) was significantly (p < 0.005) increased using 0.01 mM H2O2. O nly an increase of C-14-ADO incorporation was observed using 0.1 mM H2 O2. A concentration of 0.01 mM H2O2 reduced 5-phosphoribosyl-1-pyropho sphate synthetase (PRPP-S) activity by 60% and at the same time increa sed the activity of purine nucleoside phosphorylase, which converts in osine to hypoxanthine (PNP I), by 24%. Adenosine kinase (AK) activity was reduced by H2O2, whereas adenine phosphoribosyltransferase (APRT) activity was found to be elevated. In conclusion, the observed elevati on of cellular ATP and CP levels could be partially caused by an incre ased purine salvage resulting from changes in purine enzyme activities .