OXIDATIVE EFFECTS IN HUMAN ERYTHROCYTES CAUSED BY SOME OXIMES AND HYDROXYLAMINE

Both oximes and hydroxylamine (HYAM) are compounds with known oxidativ e capacity. We tested in vitro whether acetaldoxime (AAO), cyclohexano ne oxime (CHO), methyl ethyl ketoxime (MEKO) or HYAM affect haemoglobi n oxidation (into HbFe(3+)), formation of thiobarbituric acid reactive substances (TBARS), and glutathione (GT) depletion in human haemolysa te, erythrocytes or blood. All these parameters are known to be relate d to oxidative stress. Glutathione S-transferase (GST) activity was me asured as it may be affected by oxygen radicals. All three oximes caus ed a low degree of HbFe(3+) accumulation in erythrocytes. This was hig her in haemolysates indicating that membrane transport may be limiting or that protective mechanisms within erythrocytes are more effective. HbFe(3+) accumulation was lower for the oximes than for HYAM. AAO and HYAM caused TEARS formation in blood. For HYAM this was expected as f ree radicals are known to be generated during HbFe(3+) formation. Foe radical generation by AAO and HYAM I in erythrocytes was confirmed by the inhibition of GST. For the other two oximes (CHO and MEKO) some sp ecial effects were found. CHO did inhibit erythrocyte GST while it did not cause TEARS formation. MEKO was the least potent oxime as it caus ed no TEARS formation, little HbFe(3+) accumulation and little GST inh ibition in erythrocytes. However, GT depletion was more pronounced for MEKO than for the other oximes. indicating that glutathione conjugati on occurs. TEARS formation. GT depletion and GST modulation caused by the oximes and HYAM were also tested in rat hepatocytes. However, no e ffects were found in hepatocytes. This suggests that a factor present in erythrocytes is necessary for free radical formation. Studies with proposed metabolites of the oximes (i.e, cyclohexanone, acetaldehyde o r methylethylketone) and addition of rat liver preparations to the ery throcyte incubations with oximes, suggest that metabolism is not a lim iting factor in erythrocyte toxicity.