Effect of chromium on lipid peroxidation in isolated rat hepatocytes

To study the effects of hexavalent and trivalent chromium on lipid peroxidation, isolated rat hepatocytes were incubated with different concentrations of chromium compounds at 37°C for 60min. Lipid peroxidation was determined as thiobarbituric acid (TBA)-reacting materials. Cellular injury was observed as a leakage of lactate dehydrogenase (LDH) from hepatocytes into incubation medium. The contents of reduced glutathione(GSH) in hepatocytes were also assessed. Results obtained were as follows: (1) Lipid peroxidation of isolated rat hepatocytes which was expressed as TBA-reactant formation was inhibited by trivalent chromium at the range of concentrations tested in this experiment (125∼1000μM). Hexavalent one inhibited lipid peroxidation at low concentration (125μM), but facilitated that at high concentration (1000μM). (2) LDH-leakage was facilitated by the addition of hexavalent chromium (K2Cr2O7, 125∼1000μM), on the other hand trivalent one (Cr(NO3)3) inhibited it significantly at concentrations more than 250μM. (3) The hexavalent chromium-induced lipid peroxidation was inhibited by antioxidants such as N, N'-dipheyl-p-phenylenediamine (DPPD), α-tocopherol and diethyl dithiocarbamate (DDTC). However, LDH-leakage from hepatocytes was not inhibited by these antioxidants. (4) After the pretreatment with GSH depleting agent such as diethyl maleate (DEM) on isolated hepatocytes, the lipid peroxidation induced by hexavalent chromium was significantly enhanced and was dependent on the chromium concentrations in the incubation medium. Furthermore this enhancement of lipid peroxidation was canceled by the addition of GSH (10mM). (5) The lipid peroxidation induced by ascorbate was significantly inhibited by the addition of hexavalent chromium as well as trivalent one. This effect of hexavalent chromium might be essentially due to the reduction of hexavalent chromium to trivalent one by ascorbate. These results suggest that chromium in trivalent form inhibits lipid peroxidation in isolated hepatocytes, while hexavalent one facilitates it but is not necessarily correlated to cellular injury.