Enhanced glomerular phospholipase activity in the obstructed kidney

Previous study demonstrated that an increment of glomerular eicosanoid production may contribute to the haemodynamic changes in the obstructed kidney. To elucidate the mechanisms responsible for enhanced glomerular eicosanoid production, the present study was designed to investigate activities of related enzymes by isolated glomeruli from rat kidney with unilateral ureteral obstruction (UUO) or bilateral ureteral obstruction (BUO) for 24 hours. The activity of phospholipase A₂ (PLA₂) was determined by monitoring [¹⁴C] arachidonate release using [¹⁴C] phosphatidylcholine (PC) or [¹⁴C] phosphatidylethanolamine (PE) as a substrate. Phospholipase C (PLC) activity was assayed by measuring the release of [³H] inositol triphosphate ([³H] IP₃) from [³H] phosphatidylinositol 4,5-biphosphate ([³H] IP₂). The activity of PE-specific PLA₂ was increased in glomeruli from the kidney with BUO and the contralateral kidney of unilateral ureteral obstruction (CLK). PLC activity was significantly greater in the cytosolic fraction of glomeruli from kidneys with UUO, BUO and CLK compared to sham-operated control. The activity of PC-specific PLA₂ was not significantly increased in any group. These results indicate that the increased synthesis of eicosanoids by glomeruli from obstructed kidney may be mediated by enhanced activities of PE-specific PLA₂ and PLC. The increased activities of these phospholipases by glomeruli from CLK may contribute to a compensatory response.