Effects of isoflurane and sevoflurane on the neutrophil myeloperoxidase system of horses

Volatile anaesthestics have shown to modulate the oxidative response of polymorphonuclear neutrophils (PMNs). We investigated the effects of isoflurane and sevoflurane on the degranulation of total and active myeloperoxidase (MPO) from horse PMNs and their direct interaction with MPO activity. Whole blood from horse was incubated in 1 and 2 minimal alveolar concentrations (MAC) of isoflurane or sevoflurane for 1 h and PMNs were stimulated with cytochalasin B (CB) plus N-formyl-méthionyl-leucyl-phenylalanine (fMLP). After stimulation, the plasma was collected to measure total and active MPO by enzyme-linked immunosorbent assay (ELISA) and specific immunological extraction followed by enzymatic detection (SIEFED) respectively. The effects of 1 and 2 MAC of isoflurane and sevoflurane on the peroxidase and chlorination activity of pure MPO were assessed by fluorescence using Amplex red and 3′-(p-aminophenyl) fluorescein (APF) respectively and in parallel with a SIEFED assay to estimate the potential interaction of the anaesthetics with the enzyme. Although isoflurane and sevoflurane had inconsistent effects on total MPO release, both volatile agents reduced active MPO release and showed a direct inhibition on the peroxidase and the chlorination activity of the enzyme. A persistent interaction between MPO and anaesthetics was evidenced with isoflurane but not with sevoflurane.