Effect of zinc and copper deficiency on microsomal NADPH-dependent active oxygen generation in rat lung and liver

Both dietary zinc and copper deficiencies can cause lipid peroxidation in microsomes in rats. The cytochrome P-450 enzyme system can generate active oxygens by uncoupling of the P-450-oxy complex in the catalytic cycle and/or the electron transfer mediated by the NADPH-cytochrome P-450 reductase. The effects of dietary zinc and copper deficiencies on NADPH-dependent H2O2 generation, the catalytic activity of the cytochrome P-450 enzyme with aminopyrine as the substrate and the activity of NADPH-cytochrome P-450 reductase were determined. Zinc deficiency caused increased H2O2 production, increased NADPH-cytochrome P-450 reductase activity, decreased aminopyrine demethylation and two- and fivefold increases in iron concentration in lung and liver microsomes, respectively, compared to Zn-adequate, ad libitum--fed controls. Active oxygen generation by uncoupling of the cytochrome P-450 enzyme system and accumulation of iron are thus possible mechanisms by which zinc deficiency causes microsomal lipid peroxidation. Copper deficiency did not affect H2O2 production; however, it caused two- and fourfold increases in iron concentration in lung and liver microsomes, respectively, compared to Cu-adequate, ad libitum--fed controls. The mechanism by which cooper deficiency causes microsomal lipid peroxidation is still unknown but could be related to the observed accumulation of iron.