Plasma esterases in cystic fibrosis: the impact of a respiratory exacerbation and its treatment

Objectives: To determine the effect of an exacerbation of respiratory sympt oms in cystic fibrosis (CF) on the activities of plasma benzoylcholinestera se and butyrylcholinesterase. Methods: Twenty-nine patients with CF in a respiratory exacerbation and 27 healthy volunteers matched for age and sex were recruited. Blood was obtain ed from the patients when commencing antibiotic treatment and 14 days later on completion of treatment. One blood sample was taken from the healthy vo lunteers. The activities of benzoylcholinesterase and butyrylcholinesterase were determined by spectrophotometric assay. The circulating inflammatory markers, C-reactive protein and neutrophil elastase-alpha(1)-antiproteinase complex were also measured. Results: Benzoylcholinesterase activity was significantly (P = 0.001) lower in patients at the start of a respiratory exacerbation, compared with heal thy controls [mean (SD): 917 (274) versus 1191 (298) nmol-ml(-1).min(-1)]. Benzoylcholinesterase activity increased significantly in patients to 1013 (237) nmol.ml(-1).min(-1), following a course of antibiotic treatment (P = 0.006). Butyrylcholinesterase activity was also lower (P = 0.001) in patien ts at the start of a respiratory exacerbation, compared with healthy contro ls [5.54 (1.64) versus 7.01 (1.79) mu mol ml(-1).min(-1)], and increased si gnificantly in the patients to 6.31 (1.58) mu mol.ml(-1).min(-1) following treatment (P = 0.006). Conclusion: We demonstrated significant suppression of plasma esterase acti vities during an exacerbation of respiratory symptoms in CF, which was only partially reversed after antibiotic treatment. Further studies are needed to examine other pathways of drug metabolism in this group of chronically i nfected patients.