Journal of Lipid Research, Vol 36, 260-265, Copyright © 1995 by Lipid Research, Inc.
A possible role for platelet-activating factor in the hydrogen peroxide- induced TXB2 and PGE2 glomerular synthesis
I Arribas-Gomez, I Duque-Marin, G Perez de Lema, ML Diez-Marques, J Lucio- Cazana, M Rodriguez-Puyol and D Rodriguez-Puyol
Department of Physiology, University of Alcala de Henares, Madrid, Spain.
Hydrogen peroxide stimulates both prostanoid and platelet-activating factor
(PAF) biosynthesis in cultured rat mesangial cells and isolated rat
glomeruli. The present experiments were designed to try to establish some
relationship between prostanoid and PAF synthesis in these renal
structures, in the presence of hydrogen peroxide. Cells and glomeruli were
incubated with hydrogen peroxide under different experimental conditions,
and thromboxane B2 (TXB2), the stable metabolite of thromboxane A2 (TXA2),
and prostaglandin E2 (PGE2) concentrations were measured in the
supernatants of the cells or glomeruli. Moreover, H2O2-dependent PAF
synthesis was measured by high performance liquid chromatography (HPLC)
([3H]acetate incorporation) and radioimmunoassay. H2O2 induced increased
TXB2 and PGE2 production in cultured rat mesangial cells and isolated rat
glomeruli. This effect was blocked by incubation in the presence of a
PAF-receptor antagonist, BN-52021. This antagonist has no intrinsic effect
either in basal prostanoid synthesis or in arachidonic acid-stimulated
glomerular TXB2 synthesis. Alprazolam, another PAF antagonist,
nonchemically related to BN-52021, also completely blocked the H2O2-induced
production of TXB2 by isolated rat glomeruli. Moreover, H2O2 was also able
to induce an increased [3H]acetate incorporation into a fraction
comigrating with a PAF standard in HPLC in isolated glomeruli, and this
effect was dependent on the H2O2 concentration tested. Moreover, H2O2 was
also able to induce an increased [3H]acetate incorporation and increased
synthesis of radioimmunoassayable PAF in cultured mesangial cells. These
results suggest that the increased synthesis of PGE2 and TXB2 induced by
H2O2 could be dependent on platelet-activating factor production.