The influence of intravenous anaesthetics on the activity of enzymes released from polymorphonuclear leucocytes in vitro

Background and objective Polymorphonuclear leucocytes make a decisive contr ibution to defence against bacterial infections. In particular, the effects of anaesthetics on non-oxidative bactericidal mechanisms have previously o nly been superficially examined. Although the influence of anaesthetic agen ts on oxidative bactericidal activity has been thoroughly examined, our stu dy concentrated on the effect on nonoxidative processes, which appears to h ave been a neglected field of research. Methods The effects of methohexital, etomidate, ketamine, fentanyl and morp hine on the activity of lysozyme and beta -glucuronidase released from poly morphonuclear leucocytes have been studied in vitro. The activity of lysozy me was determined by recording the changes in the turbidity of a suspension of micrococcus lysodeicticus caused by the enzymatic action of lysozyme. b eta -glucuronidase activity was photometrically measured by the enzymatic c leavage of phenolphthalein glucuronic acid. Results High concentrations of methohexital inhibited lysozyme activity; ho wever, etomidate and morphine caused an increase of beta -glucuronidase act ivity in therapeutic plasma concentrations. While there was no effect of et omidate on lysozyme activity, all concentrations tested significantly stimu lated beta -glucuronidase activity. This result was unexpected because intr avenous anaesthetics have previously shown a tendency to suppress polymorph onuclear leucocyte functions. Whereas the inhibition of lysozyme activity b y the high concentration of methohexital was no surprise, the increase of b eta -glucuronidase activity caused by etomidate, ketamine, fentanyl and mor phine was quite unexpected. Conclusions At present, the underlying mechanism for the increase of beta - glucuronidase activity caused by etomidate, ketamine, fentanyl and morphine is unknown. The fact that there was no influence of these agents on lysozy me activity possibly suggests that the anaesthetic agents have different ef fects on azurophilic and specific granules. Since in vitro investigations h ave their limitations, it is too early to draw practical consequences from our study. Moreover, at present it is unclear whether an increase of beta - glucuronidase activity in vive is an advantage or not. In any case, we thin k it advisable to perform further investigations on the influence of anaest hetic agents on oxygen-independent bactericidal mechanisms.