Effects of enoxaparin on myeloperoxidase release during hemodialysis.

Myeloperoxidase (MPO) is a proteolytic and prooxidant enzyme largely assembled with the vascular wall, and a heparin-binding protein. We studied if low-molecular-weight heparin enoxaparin administered for hemodialysis (HD) anticoagulation causes systemic MPO activation. Plasma MPO levels were measured in patients undergoing maintenance HD with an intravenous bolus of enoxaparin. Patients were retested during HD employing dialyzers with heparin-grafted polyacrylonitrile membrane and no systemic enoxaparin administration. During enoxaparin-anticoagulated HD plasma MPO levels strikingly increased in all patients (8.6-fold at 10 minutes and 3.3-fold at 120 minutes, both P < 0.0001). The increments were directly associated with the enoxaparin dosage and strongly inversely with the predialysis levels of the enzyme. The increase in plasma MPO during systemic heparin-free HD was significantly less pronounced. Enoxaparin administered for HD anticoagulation induces a marked and dose-dependent increase in plasma MPO as a plausibly favorable result of the liberation of the enzyme from the vascular wall.