Inhibitory effect of lidocaine on the sarcoplasmic reticulum Ca2+-dependent atpase from temporalis muscle.

Myotoxic effects of local anesthetics on skeletal musclefibers involve the inhibition ofsarcoplasmic reticulum Ca2+ -dependent ATPase activity and Ca2 transport. Lidocaine is a local anesthetic frequently used to relieve the symptoms of trigeminal neuralgia. The aim of this work was to test the inhibitory and/or stimulatory effect of lidocaine on sarcoplasmic reticulum Ca2+ -dependent ATPase isolated from rabbit temporalis muscle. Ca2+ -dependent ATPase activity was determined by a colorimetric method Calcium-binding to the Ca dependent ATPase, Ca2+ transport, and phosphorylation of the enzyme by ATP were determined with radioisotopic techniques. Lidocaine inhibited the Ca2+ -dependent ATPase activity in a concentration-dependent manner. The preincubation of the sarcoplasmic reticulum membranes with lidocaine enhanced the Ca2+ dependent ATPase activity in the absence of calcium ionophore. Lidocaine also inhibited both Ca2+ uptake and enzyme phosphorylation by ATP but had no effect on Ca2+ -binding to the enzyme. We conclude that the effect of lidocaine on the sarcoplasmic reticulum Ca2+ -dependent ATPase from temporalis muscle is due to the drug's direct interaction with the enzyme and the increased permeability of the sarcoplasmic reticulum membrane to Ca.

Inhibitory effect of lidocaine on the sarcoplasmic reticulum Ca2+- dependent ATPase from temporalis muscle

Myotoxic effects of local anesthetics on skeletal muscle fibers involve the inhibition of sarcoplasmic reticulum Ca2+-dependent ATPase activity and Ca2+ transport. Lidocaine is a local anesthetic frequently used to relieve the symptoms of trigeminal neuralgia. The aim of this work was to test the inhibitory and/or stimulatory effect of lidocaine on sarcoplasmic reticulum Ca2+-dependent ATPase isolated from rabbit temporalis muscle. Ca2+-dependent ATPase activity was determined by a colorimetric method. Calcium-binding to the Ca2+- dependent ATPase, Ca2+ transport, and phosphorylation of the enzyme by ATP were determined with radioisotopic techniques. Lidocaine inhibited the Ca2+-dependent ATPase activity in a concentration- dependent manner. The preincubation of the sarcoplasmic reticulum membranes with lidocaine enhanced the Ca2+- dependent ATPase activity in the absence of calcium ionophore. Lidocaine also inhibited both Ca2+ uptake and enzyme phosphorylation by ATP but had no effect on Ca2+-binding to the enzyme. We conclude that the effect of lidocaine on the sarcoplasmic reticulum Ca2+-dependent ATPase from temporalis muscle is due to the drug's direct interaction with the enzyme and the increased permeability of the sarcoplasmic reticulum membrane to Ca.

La toxicidad de los anestesicos locales sobre las fibras musculares esqueleticas involucra a la inhibicion de la actividad de la calcio ATPasa del reticulo sarcoplasmico y a la inhibicion del transporte del calcio. Tales efectos inhibitorios no han sido aun descriptos en el musculo temporal. La lidocaina es un anestesico local habitualmente usado para aliviar los sintomas de la neuralgia del trigemino por medio de la anestesia infiltrativa de la region temporal. El objetivo del trabajo fue demostrar el efecto inhibitorio y/o activador de la lidocaina sobre la calcio ATPasa del reticulo sarcoplasmico del musculo temporal del conejo. La actividad de la calcio ATPasa se determino empleando un metodo colorimetrico. La union del calcio a la enzima, el transporte del calcio y la fosforilacion de la ATPasa por ATP se determinaron mediante el empleo de tecnicas radioisotopicas. La lidocaina inhibio a la actividad de la calcio ATPasa. El efecto inhibitorio incremento en funcion de la concentracion del anestesico. La preincubacion de las membranas del reticulo sarcoplasmico en lidocaina incremento la actividad de la calcio ATPasa en ausencia de un ionoforo de calcio. Tal resultado avala el efecto permeabilizante del anestesico local sobre las membranas del reticulo sarcoplasmico del musculo temporal. La lidocaina inhibio la captacion del calcio y la fosforilacion de la calcio ATPasa por ATP, pero no evidencio efecto sobre la union del calcio a la enzima. Concluimos que el efecto de la lidocaina sobre la calcio ATPasa del reticulo sarcoplasmico del musculo temporal se debe a la accion directa de la droga sobre la enzima y al incremento inducido de la permeabilidad de la membrana del reticulo sarcoplasmico al Ca.

Stoichiometry of ATP and metal cofactor interaction with the sarcoplasmic reticulum Ca(2+)-ATPase: a binding model accounting for radioisotopic and fluorescence results.

Sarcoplasmic reticulum Ca-ATPase belongs to the P-type ATPases family and transports calcium at the expense of ATP hydrolysis. For years, a complex pattern of activity has been observed as a function of ATP and metal cofactor concentrations, leaving the stoichiometry of both metal and ATP in the active site as an open question. In agreement with recent structural studies we present here-using Mn as analogue of Mg-radioisotopic and fluorescence results showing that two metal ions bind to the Ca-ATPase favoring ATP binding. We further show that low ATP concentration favors the binding of these ions, whereas high ATP concentration is inhibitory. We propose a binding model for ATP and metal ions, which permits simulation of our data. Finally, we suggest that (i) the contribution of two metal ions as cofactors of ATP is essential to get maximal activity; (ii) the contribution of two ATP molecules can activate or inhibit the Ca-ATPase depending on metal concentration.

Effect of carticaine on the sarcoplasmic reticulum Ca2+-adenosine triphosphatase. II. Cations dependence.

Ca2+-ATPase is a major intrinsic protein in the sarcoplasmic reticulum (SR) from skeletal muscles. It actively transports Ca2+ from the cytoplasm to the SR lumen, reducing cytoplasmic [Ca2+] to promote muscle relaxation. Carticaine is a local anesthetic widely used in operative dentistry. We previously showed that carticaine inhibits SR Ca2+-ATPase activity and the coupled Ca(2+) uptake by isolated SR vesicles, and increases the rate of Ca2+ efflux from preloaded vesicles. We also found that these effects were antagonized by divalent cations, and concluded that they were mainly due to the direct interaction of carticaine with the Ca2+-ATPase protein. Here we present additional results on the modulation of the above effects of carticaine by Ca2+ and Mg2+. The activating effect of Ca2+ on the ATPase activity is competitively inhibited by carticaine, indicating a decreased Ca2+ binding to the high affinity Ca2+ transport sites. The activating effect of Mg2+ on the phosphorylation of Ca2+-ATPase by orthophosphate is also inhibited by carticaine. The anesthetic does not affect the reaction mechanism of the cations acting as cofactors of ATP in the catalytic site. On the basis of the present and our previous results, we propose a model that describes the effect of carticaine on the Ca2+-ATPase cycle.