科研之友
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摘要
Myotoxic effects related to intracellular Ca2+ disturbances have been reported for local anesthetics. Such effects might derive from Ca-ATPase dysfunction. The aim of this work was to describe the effect of lidocaine and bupivacaine on the sarcoplasmic reticulum (SR) Ca-ATPase from fast-twitch skeletal muscle and to identify the affected steps of the enzyme's cycle. SR sealed vesicles were isolated from rabbit fast-twitch muscles by ultracentrifugation. The effect of the anesthetics on Ca-ATPase activity was assessed with a colorimetric method and Ca2+ binding, uptake, phosphorylation of the enzyme by ATP, Ca2+ dissociation kinetics and phosphoenzyme formation and decomposition levels were tested with radioisotopic methods. Lidocaine and bupivacaine inhibited Ca-ATPase activity with half-maximal inhibitory concentrations (K-i) of 25.3 and 31.4 mM, respectively, and the steady-state Ca2+ transport ability with K-i values of 33.6 and 46.5 mM, decreasing the maximal transport rate without modification of the Ca2+ or ATP affinity for the enzyme. This is consistent with an absence of competition for the transport and catalytic sites. The anesthetics did not inhibit Ca2+ binding but inhibited the phosphorylation partial reactions. Ca2+ dissociation kinetics was not affected, but the phosphoenzyme levels were decreased, and the decomposition rate of the phosphoenzyme became faster in the presence of the anesthetics. It is concluded that lidocaine and bupivacaine at concentrations available in pharmaceutical formulations for clinical medical and dental uses inhibit the SR Ca-ATPase through inhibition of key phosphorylation steps of the enzymatic cycle.
- 出版日期2014-9
