Vascular Cells Under Peroxide Induced Oxidative Stress: A Balance Study on in Vitro Peroxide Handling by Vascular Endothelial and Smooth Muscle Cells

Enzymes such as glutathione peroxidase and catalase play an important role in the cellular defence against (per) oxidative stress. Balance- and inhibitor-studies were undertaken with in vitro cultured human vascular endothelial cells (EC) and smooth muscle cells (SMC) to assay the relative importance of these enzymes in the handling of cumene hydroperoxide (Chp) and hydrogen peroxide (H2O2). Low concentrations of Chp (up to 80 μM) could be removed to near completion within the first hour of incubation by stimulation of the hexose monophosphate shunt (HMS) of both cell types. The HMS activity reached a plateau upon incubation with higher concentrations of Chp (> 80 μM). The non-converted Chp in the higher concentrations could be detected quantitatively in the incubation solution. After inhibition of the glutathione reductase by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), incubation with Chp (40 μM) did not result in a stimulation of the HMS activity. Moreover the added Chp could be recovered from the medi...