Effects of etomidate on free intracellular amino acid concentrations in polymorphonuclear leucocytes in vitro

Background: Previous studies have shown the inhibitory effects of etomidate on polymorphonuclear leucocyte (PMN) function. No reports exist, however, regarding free intracellular amino acid metabolism, although physiological cell metabolism and basic cell functions rely upon a balanced intracellular amino acid content and the cell membrane‐mediated separation of cellular amino acids from the extracellular plasma amino acid pool. Thus, in the current study, we evaluated the effects of etomidate on free intracellular amino acid metabolism in PMN. Methods: With ethics committee approval, blood was withdrawn from 35 healthy volunteers and incubated (1 h) either with 0 μg/ml, 0.0156 μg/ml, 0.0625 μg/ml or 0.5 μg/ml of etomidate as well as with its additives (propylene glycol and Lipofundin MCT® 10%). The PMN were separated using standardized Percoll®‐gradient and centrifugation procedure before deep‐freezing and lyophilization techniques were employed. All PMN samples were dissolved in methanol/H2O, and the concentrations of free intracellular amino acids were monitored using both novel advanced PMN‐separation and high‐performance liquid chromatography techniques. Results: Etomidate influenced important free amino acid profiles in PMN in a dose‐dependent manner, indicating complex changes of cellular amino acid turnover. Neither propylene glycol nor Lipofundin MCT® 10% changed free amino acid concentrations in PMN. Conclusions: For the first time, the effects of etomidate on free intracellular amino acid metabolism in PMN have been investigated. Our results draw attention to the biochemical pathways which may be involved in etomidate‐induced alterations in PMN function and cellular immunocompetence.