Involvement of phospholipase A(2) in gentamicin-induced rat mesangial cell activation

The role of the phospholipase A(2) (PLA(2)) activation in the gentamicin (Gent)-induced rat mesangial cell activation has been studied. Gent (10(-5) M) induced a time-dependent mesangial planar cell surface area reduction that was significantly inhibited by the PLA(2) inhibitors aristolochic acid (AA) and quinacrine, by the platelet-activating factor (PAF) blocker BN-52021 (BN), and by verapamil. These substances also inhibited Gent-induced [H-3]thymidine incorporation into DNA (AA, 504 +/- 20; quinacrine, 555 +/- 66; BN, 1,126 +/- 120; and verapamil, 896 +/- 109; vs. 1,818 +/- 35 cpm/well in cells treated with Gent alone) and the Gent-induced increase in cell number (AA, 20,116 +/- 2,696; quinacrine, 24,687 +/- 1,481; BN, 26,122 +/- 1,016; and verapamil, 27,566 +/- 1,214; vs. 47,486 +/- 1,124 cells/well in cells treated with Gent alone). Gent induced a twofold increase in [H-3]acetate incorporation into PAF (27 +/- 3 vs. 12 +/- 2 cpm/mu g protein in control conditions) that was completely blocked by AA, BN, or verapamil. Gent increased thromboxane B-2 and prostaglandin E-2 (PGE(2)) production, with both increases inhibited by either AA or verapamil. BN only inhibited the Gent-induced mesangial PGE(2) production. In addition, Gent increased PLA(2) activity (measured as [H-3]arachidonic acid release, 29,849 +/- 2,151 vs. 20,104 +/- 2,308 cpm/well in basal conditions), an effect that was blocked by AA (11,804 +/- 684 cpm/well). These data suggest a major role for PLA(2) activation in Gent-induced mesangial cell contraction, proliferation and prostanoid secretion.