Prostaglandin and thromboxane synthesis by rat glomerular epithelial cells

Abstract

Isolated rat glomeruli have been shown to synthesize prostaglandin (PG) and thromboxane (Tx). In this study, we evaluated, by radioimmunoassay and radiochromatographic methods, PG and Tx synthesis by glomerular cells in culture. Transmission and scanning electron microscopy showed polygonal cells, attached by desmosomes, with surface microvilli. These features are typical of glomerular epithelial cells. Incubation of these glomerular epithelial cells with arachidonic acid (C20:4) resulted in an array of endproducts with concentrations of PGE2 greater than TxB2 greater than PGF2 alpha greater than 6-keto-PGF1 alpha . Addition of angiotensin II (AII) to the cultured glomerular cell produced almost exclusive stimulation of PGE2 with PGE2 much much greater than PGF2 alpha greater than TxB2 = 6-keto-PGF1 alpha . AII and AIII (100 micrometer to 1 micrometer ) stimulated PGE2 in glomerular epithelial cells, and the increments of PGE2, as a function of the concentration of AII or AIII, were similar. The sar1-thr8-AII analog inhibited both AII- and AIII-stimulated PGE2 synthesis. The divalent cation ionophore A23187 in concentrations of 0.2 to 2.0 micrometer increased primarily PGE2 and TxB2 synthesis with smaller increases of PGF2 alpha and 6-keto-PGF1 alpha . The relative concentrations of PG and Tx produced by rat glomerular epithelial cells, incubated with C20:4 or A23187, were similar. Our results demonstrate that: (1) the predominant cell grown in culture from the rat glomerulus, after 9 days, is the epithelial cell; (2) this cell is capable of PG and Tx synthesis; (3) stimulation of PG by AII and AIII may be mediated by the same cellular receptor, AII and AIII increase primarily the synthesis of a vasodilatory PG, PGE2; (4) exogenous substrate C20:4 or release of endogenous C20:4 by the divalent cation ionophore A23187 not only stimulates PGE2 but also the vasoconstrictor TxA2; and (5) the PG and Tx endproducts synthesized by epithelial cells may be determined by an intracellular coupling of the specific synthetic enzymes with different pools of C20:4.