Alloxan cytotoxicity is highly potentiated by plasma membrane- and lysosomal-associated iron : a study on a model system of cultured J-774 cells

摘要: Pancreatic islet beta cells, and some other cell types, are sensitive to the damaging effects of alloxan. The mechanisms behind cytotoxicity have not been fully elucidated, although they considered be mediated by formation reactive oxygen metabolites. In present study, cytotoxic alloxan/cysteine at high low concentrations were investigated on a model system cultured J-774 cells. Viability was estimated trypan blue dye exclusion test, plasma membrane permeability modified microfluometric fluorescein diacetate technique lysosomal stability microfluorometric acridine orange method. results showed: (a) hydrogen peroxide, readily diffusing through cellular membranes produced extracellularly in large amounts concentrations, enters secondary lysosomes if previously degraded anti-oxidant systems. Intralysosomal Fenton reactions, with hydroxyl radicals, may induced provided catalytically active iron is present. This would result damage followed leakage contents sap degeneration. (b) Alloxan/cysteine production superoxide peroxide which caused almost no appeared non-toxic unless there membrane-associated iron. Consequently, cells initially allowed endocytose during culture, or briefly exposed just before exposure alloxan cysteine, showed greatly enhanced sensitivity. this case iron, combination believed give rise radical (Fenton reaction) resultant loss integrity. We thus propose that reasons for pronounced sensitivity include weak anti-oxidative defense systems especially vulnerable ironcatalysed following exocytosis transition metal.