Lidocaine inhibits potassium efflux and hemolysis in erythrocytes during oxidative stress in vitro

Lidocaine is a widely used local anesthetic agent. The aim of this work was to study the action of lidocaine on human red blood cells exposed to an ox idative stress in vitro. Blood was obtained from healthy volunteers. After separation from plasma, the erythrocytes were suspended in phosphate buffer . Oxidative stress was induced by incubation with a free radical generator, the 2,2' azobis (2-amidinopropane) hydrochloride (AAPH). Erythrocytes were incubated with or without lidocaine at two concentrations (36.93 and 73.85 muM) and with or without AAPH (20 mM). Electron paramagnetic resonance (EP R) spectroscopy was performed to identify the free radical species generate d by AAPH using the spin trap 5-5'-dimethyI-L-pyroline-N-oxide (DMPO). Diff erent sets of experiments were run. Potassium efflux was measured by flame photometry in each group at time 0 min and every 30 min of the experiment f or 2 h. Hemolysis was studied by the Drabkin method at increasing concentra tions of AAPH (20, 50, and 100 mM) and with or without lidocaine (36.93 muM ). The oxygen radical absorbance capacity (ORAC) was measured by using allo phycocyanin (APC) as a fluorescent indicator protein, and the antioxidant c apacity of lidocaine (36.93 muM) was studied by the analysis of fluorescenc e of the APC. AAPH was shown to produce alkoxyl free radicals. Oxidative st ress induced a marked increase in the potassium efflux and the hemolysis th at was AAPH dose-dependent. Lidocaine inhibited the potassium efflux and de layed the occurrence of hemolysis. Lidocaine did not show any antioxidant p roperties for the free radical species generated by AAPH. In this model, li docaine protects erythrocytes against oxidative stress. This effect is not explained by a free radical scavenging property. The results may be of grea t interest in clinical practice such as intravenous regional anesthesia or the prevention of ischemia-reperfusion injury. (C) 2000 Elsevier Science In c. All rights reserved.