INTERACTION OF HYPOCHLORITE WITH HYDROPEROXIDAS AND OTHER OXIDATION-PRODUCTS OF PHOSPHATIDYLCHOLINE LIPOSOMES

The interactions of hypochlorite (HOCl/OCl-) with organic peroxides (t ert-butyl hydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide, tert-butyl perbenzoate, and dibenzoyl peroxide) or epoxides (cis- and trans-2,3-epoxybutane, cholesterol 5 alpha,6 alpha-epoxide, and cis-9 ,10-epoxystearic acid), as well as with oxidized or non-oxidized lipos omes from egg yolk phosphatidylcholine (containing lipid peroxidation products) have been studied. The reduction of HOCl/OCl- was measured u sing luminol chemiluminescence. The rate constant of the reaction of H OCl/OCl- with liposomes was directly proportional to the content of TE A-reactive lipid peroxidation (LPO) products (lipid hydroperoxides and aldehydes). Hypochlorite did not react with saturated dimyristoylphos phatidylcholine (DMPC), and the reduction of phosphatidylcholine doubl e bonds occurred at the same rate in both oxidized and non-oxidized li posomes. Therefore, it is precisely LPO products that reacted with HOC l/OCl-. None of the epoxides tested reacted with hypochlorite, nor did di-tert-butyl peroxide, tert-butyl perbenzoate, and dibenzoyl peroxid e (all the compounds were incorporated into DMPC liposomes). The rever se was the case of tert-butyl hydroperoxide and cumene hydroperoxide, which effectively reacted with hypochlorite. The results indicate that the initiation of hypochlorite-induced LPO involves neither peroxides (dialkyl, diacyl, and alkylacyl) nor epoxides. Organic hydroperoxides , commonly present in the lipid phase of biological membranes under in vivo conditions, appear to be LPO intermediates. For example, the int eraction of hydroperoxides with hypochlorite could result in the forma tion of free radicals and subsequent accumulation of LPO products.