Lipid peroxidation and its inhibition by tinoridine, II. Ascorbic acid-induced lipid peroxidation of rat liver mitochondria.

Incubation of rat liver mitochondrial suspension with ascorbic acid and Fe2+ resulted in the formation of malondialdehyde and a decrease in the turbidity of the suspension. The maximum amount of malondialdehyde formed during the peroxidation reaction was estimated to be 1 mol per approximately 6 mol of mitochondrial phospholipids. Tinoridine and alpha-tocopherol at the concentration of 5 micron and 1 mM, respectively, completely inhibited the peroxidative disintegration of mitochondria. From the relationship between the concentration of tinoridine and the amount of malondialdehyde formed, it was demonstrated that 1 mol of tinoridine prevents the formation of about 6 mol of malondialdehyde. These findings suggest that there is a limit in the chain reaction of the lipid peroxidation of mitochondria and that the limit is the membrane sphere which is capable of releasing 6 molecules of malondialdehyde and contains about 36 molecules of the constitutive phospholipids.