Rat hindlimb joint immobilization with acrylic resin orthoses

Abstract

The objective of the present study was to propose an orthosis of light material that would be functional for the animal and that would maintain only the ankle joint immobilized. Male Wistar rats (3 to 4 months old, 250-300 g) were divided into 2 groups (N = 6): control and immobilized for 7 days. Rats were anesthetized with sodium pentobarbital (40 mg/kg weight) and the left hindlimb was immobilized with the orthoses composed of acrylic resin model, abdominal belt and lateral supports. The following analyses were performed: glycogen content of the soleus, extensor digitorum longus, white gastrocnemius, red gastrocnemius, and tibialis anterior muscles by the phenol sulfuric method, and the weight, fiber area and intramuscular connective tissue of the soleus by the planimetric system. Data were analyzed statistically by the Kolmogorov-Smirnov, Student t and Wilcoxon tests. Immobilization decreased glycogen in all muscles (P < 0.05; soleus: 31.6%, white gastrocnemius: 56.6%, red gastrocnemius: 39%, extensor digitorum longus: 41.7%, tibialis anterior: 45.2%) in addition to reducing soleus weight by 34% (P < 0.05). Furthermore, immobilization promoted reduction of the fiber area (43%, P < 0.05) and increased the connective tissue (200%, P < 0.05). The orthosis model was efficient comparing with another alternative immobilization model, like plaster casts, in promoting skeletal muscle alterations, indicating that it could be used as a new model in other studies related to muscle disuse.

Metformina minimiza as alterações morfométricas no músculo sóleo de ratos submetidos à imobilização articular

“…Para a imobilização, os ratos foram anestesiados com pentobarbital sódico (50mg/kg), tendo a pata posterior esquerda imobilizada com órtese de resina acrílica durante sete dias, a qual manteve a articulação do tornozelo em posição neutra (90º), deixando as articulações do joelho e quadril livres (13) . A metformina foi diluída na água disponível durante sete dias para os animais na concentração de 1.4µg.ml -1 , realizando-se a troca do frasco de âmbar a cada 48 horas (9) .…”

Efeitos do ultrassom terapêutico associados ao alongamento estático sobre parâmetros histomorfométricos longitudinais de sóleos imobilizados de ratos

“…A short immobilization period (seven days) is already enough for the muscle to suffer morphometric and mechanical adaptations, such as reduction of muscular mass and length, number of sarcomeres, increase of the conjunctive tissue density and reduction of the maximum resistance of muscular rupture [2][3][4] . Increase of conjunctive tissue induces to abnormal crossed ligations of conjunctive tissue fibers, which results in fast muscular stiffness and reduction of range of motion 1,5 .…”

The effect of a low dose of clenbuterol on rat soleus muscle submitted to joint immobilization

“…Although it is fre-Clenbuterol prevents muscular atrophy www.bjournal.com.br quently necessary, immobilization is accompanied by side effects, such as muscular cell atrophy, intramuscular fibrosis, loss of muscle extensibility, and limitations in joint motion (7). Several studies have demonstrated that concomitant with muscular hypotrophy, great modifications occur in skeletal muscle homeostasis, affecting myofibrillar protein synthesis, contractile dynamics as well as the effectiveness of metabolic signals, that can lead to a reduction in glycogen reserves, force and fatigue resistance (4,8,9).…”