Sevoflurane inhibits equine myeloperoxidase release and activity in vitro.

Objective To investigate the effects of the volatile anaesthetic sevoflurane on the release of total and active myeloperoxidase (MPO) by non-stimulated and stimulated polymorphonuclear neutrophils (PMNs) in whole blood from healthy horses. Study design In vitro experimental study. Animals Adult healthy horses. Methods Samples of whole venous blood were collected and incubated in air or in air plus 2.3% or 4.6% sevoflurane for 1 hour. PMNs were stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP), with a combination of cytochalasin B (CB) and fMLP or with phorbol myristate acetate (PMA). Total and active MPO contents released by PMNs in blood were measured by enzyme-linked immunosorbent assay (ELISA) and specific immunological extraction followed by enzymatic detection (SIEFED) respectively. Additional experiments were performed to assess the effect of sevoflurane on the peroxidase and chlorination cycles of purified equine MPO using Amplex Red and 3'-(p-aminophenyl) fluorescein as fluorogenic substrates respectively. Results As compared with air alone, 1 hour exposure of whole blood to 4.6% sevoflurane in air significantly inhibited the release of total and active MPO by unstimulated and both fMLP- and CB + fMLP-stimulated PMNs but not by PMA-stimulated PMNs. Although 2.3% sevoflurane had no effect on total MPO release by unstimulated and stimulated PMNs, it significantly reduced the release of active MPO by unstimulated and fMLP-stimulated PMNs. Additionally, sevoflurane reversibly inhibited the activity of MPO, especially the peroxidase cycle of the enzyme. Conclusions and clinical relevance Although our experimental study was not designed to assess the effects of sevoflurane in vivo, this inhibition of MPO release and activity may have relevance for anaesthetized horses and deserves further studies to examine the clinical importance of these findings.