CONICET | Buscador de Institutos y Recursos Humanos

Retina is highly susceptible to oxidative damage due to its high content of polyunsaturated fatty acids (PUFAs), mainly docosahexaenoic acid (22:6 n3). Lipid peroxidation process is thought to be involved in many physiological and pathological events. Many model membranes can be used to learn more about issues that can not be studied in biological membranes. Sonicated (SL) and non-sonicated (NSL) liposomes prepared with lipids isolated from bovine retina and characterized by dynamic light-scattering, were submitted to lipid peroxidation, under air atmosphere at 22 °C, with Fe2+ or Fe3+ as initiator, in different aqueous media. Conjugated dienes and trienes, determined by absorption at 234 and 270 nm respectively, and thiobarbituric acid-reactive substances were measured as a function of time. Peroxidation of SL or NSL liposomes initiated with 25 ìM FeSO4 in 20 mM Tris-HCl pH 7.4 resulted in an increase in TBARS production after a lag phase of 60 min. Incubation of both types of liposomes in water resulted in shortening of the lag phase at 30 min. When lipid peroxidation was performed in 0.15 M NaCl, lag phase completely disappeared. On the other hand, FeCl3 (25 ìM) induced a limited production of TBARS only just after 30 min of incubation. When Fe2+- or Fe3+- lipid peroxidation of both types of liposomes was carried out in water or 0.15 M NaCl, formation of conjugated dienes and conjugated trienes were higher than in reactions carried out in 20 mM Tris-HCl pH 7.4. Our results established that both liposome types were susceptible to Fe2+-initiated lipid peroxidation and they were peroxidized in a lesser extent by Fe3+. We verified that lipid peroxidation of retinal liposomes is affected not only by type of initiator but also by aqueous media. This model constitutes a useful system to study formation of lipid peroxidation intermediaries and products in an aqueous environment.