Phospholipase A2 from Daboia siamensis venom induces acute kidney injury: involvement of ion channels in an isolated perfused rabbit kidney model.

Abstract

Background: Acute kidney injury (AKI) is a serious complication associated with Daboia siamensis envenomation, primarily due to direct nephrotoxicity. This study aimed to investigate the effects of the phospholipase A₂ (RvPLA₂) fraction from D. siamensis venom on renal function and to assess whether pretreatment with ion channel blockers could mitigate these effects using an isolated perfused kidney (IPK) model.

Methods: Twenty IPKs were allocated into five groups (n = 4 each): (1) RvPLA₂ in calcium-deficient modified Krebs-Henseleit solution (MKHS), (2) RvPLA₂ in standard MKHS, (3) RvPLA₂ following pretreatment with verapamil (a voltage-gated Ca²⁺ channel blocker), (4) RvPLA₂ following pretreatment with amiloride (a Na⁺ channel blocker), and (5) RvPLA₂ following pretreatment with minoxidil (a KATP channel opener). Renal function parameters were assessed accordingly.

Results: Administration of 280 μg of RvPLA₂ in calcium-deficient MKHS caused no significant changes in renal function. In contrast, RvPLA₂ in standard MKHS (1.9 mM Ca²⁺) significantly increased perfusion pressure (PP), renal vascular resistance (RVR), and free water excretion (p < 0.05), while non-significant increases were observed in glomerular filtration rate (GFR), urinary flow rate (UF), osmolar clearance (C_osm), and the fractional excretion of sodium (FE_Na⁺) and potassium (FE_K⁺). Verapamil alone caused significant increases in GFR and C_osm (p < 0.05) and non-significant increases in PP, RVR, UF, FE_Na⁺, and free water excretion. Amiloride and minoxidil alone did not alter renal function. Pretreatment with verapamil, amiloride, or minoxidil failed to prevent the renal functional changes induced by RvPLA₂.

Conclusions: The RvPLA₂ activity requires Ca²⁺ for activation which may target distinct sites on the cell membrane, including ion channel receptors in nephrons. The effects of RvPLA₂ on glomerular and renal tubular function are independent and cannot be modified by pretreatment with different ion channel blockers.