The alkaline single cell gel electrophoresis comet. assay was applied to study genotoxic properties of two inhalation
anesthetics—halothane and isoflurane—in human peripheral blood lymphocytes PBL.. The cells were exposed in vitro to
either halothane 2-bromo-2-chloro-1,1,1-trifluoroethane. or isoflurane 1-chloro-2,2,2-trifluoroethyl difluoromethyl ether. at
concentrations 0.1–10 mM in DMSO. The anesthetics-induced DNA strand breaks as well as alkali-labile sites were
measured as total comet length i.e., increase of a DNA migration.. Both analysed drugs were capable of increasing DNA
migration in a dose-dependent manner. In experiments conducted at two different electrophoretic conditions 0.56 and 0.78
Vrcm., halothane was able to increase DNA migration to a higher extent than isoflurane. The comet assay detects DNA
strand breaks induced directly by genotoxic agents as well as DNA degradation due to cell death. For this reason a
contribution of toxicity in the observed effects was examined. We tested whether the exposed PBL were able to repair
halothane- and isoflurane-induced DNA damage. The treated cells were incubated in a drug-free medium at 378C for 120
min to allow processing of the induced DNA damage. PBL exposed to isoflurane at 1 mM were able to complete repair
within 60 min whereas for halothane a similar result was obtained at a concentration lower by one order of magnitude: the
cells exposed to halothane at 1 mM removed the damage within 120 min only partly. We conclude that the increase of DNA
migration induced in PBL by isoflurane at 1 mM and by halothane at 0.1 mM was not a result of cell death-associated DNA
degradation but was caused by genotoxic action of the drugs. The DNA damage detected after the exposure to halothane at 1
mM was in part a result of DNA fragmentation due to cell death.