The protection by ascorbate and glutathione against microsomal lipid peroxidation is dependent on vitamin E.
Lipid peroxidation of rat liver microsomal fractions was monitored by its low-level chemiluminescence in preparations from controls and vitamin-E-deficient animals. Measurements were made (a) of the duration of the lag phase tau0 after initiation with NADPH/iron-ADP and (b) of the slope of the chemiluminescence increase. In microsomes with normal vitamin E (alpha-tocopherol) level the lag phase tau0 was substantially increased by ascorbate; in contrast, even an enhanced peroxidation was observed with ascorbate in vitamin-E-deficient microsomes. Therefore, the ascorbate-mediated protection of microsomal membranes against lipid peroxidation is dependent on vitamin E in the membrane. In vitamin E deficiency the pro-oxidant effect of ascorbate was abolished when glutathione (GSH) was present. Likewise, GSH does not prolong the lag phase tau0 in vitamin E deficiency. However, GSH (but not cysteine) exerts an antioxidant effect both in controls and in vitamin E deficiency by decreasing the slope of the chemiluminescence increase during lipid peroxidation. The involvement of GSH in an enzyme-dependent mechanism is suggested.
Wefers
H
H
Institut für Physiologische Chemie I, Universität Düsseldorf, Federal Republic of Germany.
Sies
H
H
D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D003545:Cysteine / Q000494:pharmacology; D005978:Glutathione / Q000494:pharmacology*; D008054:Lipid Peroxides / Q000096:biosynthesis*; D008163:Luminescent Measurements; D008862:Microsomes, Liver / Q000378:metabolism*; D051381:Rats; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D014810:Vitamin E / Q000494:pharmacology*; D014811:Vitamin E Deficiency / Q000378:metabolism*
D008054:Lipid Peroxides; D013438:Sulfhydryl Compounds; D014810:Vitamin E; D005978:Glutathione; D003545:Cysteine; D001205:Ascorbic Acid