Superoxide production by porcine retinal pigment epithelium in vitro

Cultured porcine retinal pigment epithelial cells release superoxide, measured as superoxide dismutase (SOD)-suppressible reduction of cytochrome C, and SOD-suppressible luminol-dependent chemiluminescence. Latex beads stimulated a significant release of superoxide that reached 82 nmol/mg protein in the first 15 min and declined thereafter. Formation of an insoluble blue formazan following reduction of nitroblue tetrazolium histochemically demonstrated that superoxide was released over the region of the cell vicinal to the bead. Dioctanoylglycerol, a synthetic, cell-permeating activator of protein kinase C, also elicited a rapid release of superoxide from RPE cells. This study emphasizes the need to characterize the mechanisms by which superoxide is generated, whether its release is regulated, and how toxicity is prevented in vivo.