[Effects of local anesthetics upon human natural killer cytotoxicity in vitro]

Effects of 3 local anesthetics, bupivacaine, mepivacaine and lidocaine, upon natural killer cytotoxicity were studied in vitro. Mononuclear cell layer was recovered by Ficoll-Paque sedimentation from heparinized venous blood obtained prior to the induction of anesthesia. The mononuclear cells were divided into three groups: control group was incubated in medium only: low concentration group incubated in medium with 2.0 micrograms.ml-1 of mepivacaine (n = 20) or lidocaine (n = 20), or 0.5 micrograms.ml-1 of bupivacaine (n = 21); high concentration group in medium with 20 micrograms.ml-1 of mepivacaine or lidocaine, or 5 micrograms.ml-1 of bupivacaine. These three groups were incubated simultaneously in humidified atmosphere with 5% CO2 in incubator for 2 hours. NK cell cytotoxicity was determined in a chromium release assay against K 562 cell as a target cell. An effector to target cell ratio of 40:1 was used. Comparison among 3 local anesthetics showed no significant difference at high concentration, but a significant difference at low concentration. This was due to the differences between bupivacaine and lidocaine. Neither bupivacaine nor mepivacaine inhibited % NK cytotoxicity at both low and high concentrations compared with control. Lidocaine significantly inhibited % NK cytotoxicity at low concentration, but did not inhibit at high concentration compared with control. We concluded that neither bupivacaine nor mepivacaine inhibited % NK cytotoxicity at concentration of clinical dose compared with control in vitro, but lidocaine inhibited % NK cytotoxicity at a concentration of 2.0 micrograms.ml-1 compared with control.