Stimulation by oxygen radicals of prostaglandin production by rat renal glomeruli

Abstract

Polymorphonuclear leukocytes secreting oxygen radicals are found in the glomerular capillaries at an early stage of experimental acute glomerulonephritis. The aim of this work was to study the effects of these radicals on prostaglandin (PG) production by the glomeruli. Glomeruli were isolated from rat renal cortex and incubated in the presence of a biochemical system capable of generating oxygen radicals (addition to 100 microM xanthine of increasing concentrations of xanthine oxidase). Synthesis of PGE2, PGF2alpha, 6 keto PGF1alpha, and TXB2 estimated using specific radioimmunoassays was twofold greater in the presence of oxygen radicals. This effect was inhibited by catalase, slightly stimulated by superoxide dismutase, unaffected by hydroxyl radical scavengers, thus suggesting that hydrogen peroxide was the by-product responsible. This was confirmed by the stimulatory effect of hydrogen peroxide itself (1 to 100 microM) on PG synthesis. The effect of mepacrine, an inhibitor of phospholipase activity, on PG production was more marked in the presence of hydrogen peroxide and the stimulation of PG synthesis by hydrogen peroxide or oxygen radicals was progressively inhibited in the presence of arachidonic acid. Moreover, oxygen radicals stimulated the release of 14C-arachidonic acid previously incorporated in isolated glomeruli. This demonstrates that the increase in PG synthesis in response to oxygen radicals is due to activation of glomerular phospholipase by these radicals. This effect that is likely to occur at an early stage of experimental glomerulonephritis could play a role in the mechanism of the inflammatory process.