Effect of aqueous acetone extractions and vitamin E on nadph-dependent lipid peroxidation of sheep and rat liver microsomes

Abstract

1. 1. Extraction of sheep ( Ovis aries) liver microsomes with acetone : water 100 :4 (v/v), acetone : water 100 : 7 (v/v) and acetone : water 90 :10 (v/v) removed 25, 44 and 60%, respectively, of the organic phosphorus. 2. 2. Extraction of rat ( Rattus norvegicus) liver microsomes with acetone : water 100 :4 (v/v) caused a 5 % increase in the organic phosphorus content. 3. 3. The removal of 25, 44 and 60% of the organic phosphorus from sheep liver microsomes caused losses of NADPH-dependent lipid peroxidation activity that were far larger than the removal of phospholipid substrate would cause. Increasing the organic phosphorus content of rat liver microsomes by 5 % caused a slight increase in NADPH-dependent lipid peroxidation activity. 4. 4. The phospholipid compositions of the aqueous acetone extracts of sheep liver microsomes were similar to that of the total microsomal lipid extract. 5. 5. The hypothesis is put forward that NADPH-dependent lipid peroxidation has a structural phospholipid requirement and that more than one protein is involved in this enzymic process. 6. 6. Liver microsomes from rats fed 600 mg α-tocopheryl acetate/kg diet possessed negligible NADPH-dependent lipid peroxidation activity. Extraction of these microsomes with acetone : water 100 :4 (v/v) reversed the inhibition of NADPH-dependent lipid peroxidation by dietary vitamin E.