Expression of sarcoplasmic-endoplasmic reticulum Ca-ATPase isoforms in masticatory muscles.

The aim of this study was to characterize the sarcoplasmic-endoplasmic reticulum Ca-ATPase (SERCA) isoforms in rabbit masticatory muscles compared with those in fast-twitch muscle. It was hypothesized that combined expression of the SERCA isoforms in fast- and slow-twitch muscles accounts for lower Ca-ATPase activity. SERCA was isolated by differential centrifugation, the isoforms were determined by ELISA, and the activity of each isoform was measured using a colorimetric method. Activity was tested for significance by anova, and the distribution of isoforms was assessed using the chi-square test (P < 0.05) and correlated to SERCA activity using Spearman's rank correlation. SERCA1 was predominant (90.5%) in fast-twitch muscle, whereas a mixture of SERCA isoforms was found in masticatory muscles: 62-78% was SERCA2, 20-37% was SERCA1, and the SERCA3 content was negligible. Depressor muscles showed a significantly higher content (77.8%) of SERCA2, and elevator muscles showed a higher content (35.4%) of SERCA1. Elevator muscles showed higher expression of SERCA2a (58%), and depressor muscles showed higher expression of SERCA2b (20%). The SERCA1 content was mainly SERCA1a and significantly higher for elevator muscles (33%), whereas depressor muscles showed a higher content of SERCA1b (4%). The SERCA1 content of fast-twitch muscle was mainly SERCA1a (88.5%). It is concluded that the mixture of different SERCA isoforms, along with a substantial content of SERCA2b, in masticatory muscles would support lower Ca-ATPase activity and calcium transport.

Effect of articaine on calcium transport in sarcoplasmic reticulum membranes isolated from medial pterygoid muscle.

Local anesthetics used in dentistry have myotoxic effects. Articaine, also known as carticaine, is one of the local anesthetics most widely used in clinical dentistry. The aim of this work was to describe its effect on the sarcoplasmic reticulum Ca-ATPase isolated from medial pterygoid muscle. Ca-ATPase enzymatic activity was determined by a colorimetric method and ATP-dependent calcium uptake with a radioisotopic technique. Articaine inhibited both Ca-ATPase activity and calcium uptake in a concentration-dependent manner. Both inhibitory effects became evident at articaine concentrations lower than those employed in clinical dentistry. Half-maximal inhibitory concentrations (K) were 15.1 +/- 1.8 mM (n = 6) and 25.2 +/- 1.6 mM (n = 6) for enzymatic activity and calcium uptake, respectively. Preincubation of sarcoplasmic reticulum membranes with articaine enhanced Ca-ATPase activity in the absence of calcium ionophore, suggesting an ionophoric-like effect of the local anesthetic. We conclude that the inhibitory effect of articaine on the sarcoplasmic reticulum Ca-ATPase isolated from medial pterygoid muscle is due to a direct interaction of the anesthetic with the enzyme and to the increased membrane permeability to calcium induced by this drug.

Effect of articaine on calcium transport in sarcoplasmic reticulum membranes isolated from medial pterygoid muscle

Local anesthetics used in dentistry have myotoxic effects. Articaine, also known as carticaine, is one of the local anesthetics most widely used in clinical dentistry. The aim of this work was to describe its effect on the sarcoplasmic reticulum Ca-ATPase isolated from medial pterygoid muscle. Ca-ATPase enzymatic activity was determined by a colorimetric method and ATP-dependent calcium uptake with a radioisotopic technique. Articaine inhibited both Ca-ATPase activity and calcium uptake in a concentrationdependent manner. Both inhibitory effects became evident at articaine concentrations lower than those employed in clinical dentistry. Half-maximal inhibitory concentrations (Ki) were 15.1± 1.8 mM (n = 6) and 25.2 ± 1.6 mM (n = 6) for enzymatic activity and calcium uptake, respectively. Preincubation of sarcoplasmic reticulum membranes with articaine enhanced Ca-ATPase activity in the absence of calcium ionophore, suggesting an ionophoriclike effect of the local anesthetic. We conclude that the inhibitory effect of articaine on the sarcoplasmic reticulum Ca-ATPase isolated from medial pterygoid muscle is due to a direct interaction of the anesthetic with the enzyme and to the increased membrane permeability to calcium induced by this drug.

Los anestésicos locales de uso odontológico tienen efectos miotóxicos. La carticaína, también conocida como articaína, es uno de los anestésicos locales más usados en la clínica odontológica actual. El objetivo del trabajo fue describir el efecto de la carticaína sobre la Ca-ATPasa del retículo sarcoplásmico aislada del músculo pterigoideo interno. La actividad enzimática de la bomba de calcio se determinó por un método colorimétrico y se utilizó un método radioisotópico a fin de determinar la captación de calcio dependiente de ATP. La carticaína inhibió la actividad enzimática y la captación de calcio en función de su concentración. Ambos efectos se observaron a concentraciones de carticaína menores a las utilizadas en la clínica. Las concentraciones de carticaína necesarias para inhibir la actividad Ca-ATPásica y la captación de calcio a la mitad de su valor máximo (Ki) fueron 15.1 ± 1.8 mM (n = 6) y 25.2 ± 1.6 mM (n = 6) respectivamente. La preincubación con carticaína de las membranas de retículo sarcoplásmico del músculo pterigoideo interno, en ausencia de ionóforo de calcio, incrementó la actividad de la enzima, evidenciando un efecto ionofórico del anestésico local. Concluimos que el efecto inhibitorio de la carticaína sobre la Ca-ATPasa de retículo sarcoplásmico del músculo pterigoideo interno se debe a la acción directa del anestésico local sobre la enzima y al incremento de la permeabilidad de la membrana del retículo sarcoplásmico al calcio inducido por esta droga.