[Inhibitory effects of serotonin and sodium ascorbate on the oxidative aggregation of lipoproteins]

Milk lipoproteins (MLPs) are structurally and biochemically similar to blood lipoproteins, which allow the former to be used as model objects for studying the properties of the latter. The results of turbidimetric measurements showed a change in the light scattering from MLP suspensions upon contact with Fe3+ ions in the free from or in chelate complexes with o-phenanthroline and EDTA. No such effect was observed for Fe2+ ions. The effect of Cu2+ ions (in microscopic amounts) was similar to that of Fe3+, while Ca2+ and Mg2+ produce no effect. It was found that 1,1-azabicyclohexanecarbonitrile-2-methylpropionamidine dihydrochloride (an azoinitiator capable of spontaneous decomposition with the formation of peroxide radicals in an oxygen containing-medium) introduced into an MLP suspension produces the same effect as Fe3+ and Cu2+ ions. Study of the particle size distribution in a microcapillary by the method of impedance measurements showed that a change in the light scattering from the suspension is caused by the MLP aggregation. The action of aggregation factors upon the MLPs led to their oxidation, as indicated by accumulation of the TBA-active products. The ability of copper ions to oxidize MLPs agrees with the data reported on the copper-ion-induced oxidation of blood lipoproteins, which was observed in studying a relationship between this oxidation and clinical manifestations of atherosclerosis. Thus, pronounced oxidation of both milk an blood lipoproteins in the presence of microscopic amounts of copper ions is indicative of a similarity of these processes. The process of lipoprotein aggregation induced by various oxidizing agents is inhibited by sodium ascorbate and serotonin. At the same time, beta-naphthol (an antioxidant soluble in lipids) does not affect the aggregation process. It is suggested that the oxidative aggregation of lipoproteins mag be related to the problem of atherogenesis and thrombogenesis.