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

Abstract

The aim of the present study was to evaluate the effect of joint immobilization on morphometric parameters and glycogen content of soleus muscle treated with clenbuterol. Male Wistar (3-4 months old) rats were divided into 4 groups (N = 6 for each group): control, clenbuterol, immobilized, and immobilized treated with clenbuterol. Immobilization was performed with acrylic resin orthoses and 10 µg/kg body weight clenbuterol was administered subcutaneously for 7 days. The following parameters were measured the next day on soleus muscle: weight, glycogen content, cross-sectional area, and connective tissue content. The clenbuterol group showed an increase in glycogen (81.6%, 0.38 ± 0.09 vs 0.69 ± 0.06 mg/100 g; P < 0.05) without alteration in weight, cross-sectional area or connective tissue compared with the control group. The immobilized group showed a reduction in muscle weight (34.2%, 123.5 ± 5.3 vs 81.3 ± 4.6 mg; P < 0.05), glycogen content (31.6%, 0.38 ± 0.09 vs 0.26 ± 0.05 mg/100 mg; P < 0.05) and cross-sectional area (44.1%, 2574.9 ± 560.2 vs 1438.1 ± 352.2 µm 2 ; P < 0.05) and an increase in connective tissue (216.5%, 8.82 ± 3.55 vs 27.92 ± 5.36%; P < 0.05). However, the immobilized + clenbuterol group showed an increase in weight (15.9%; 81.3 ± 4.6 vs 94.2 ± 4.3 mg; P < 0.05), glycogen content (92.3%, 0.26 ± 0.05 vs 0.50 ± 0.17 mg/100 mg; P < 0.05), and cross-sectional area (19.9%, 1438.1 ± 352.2 vs 1724.8 ± 365.5 µm 2 ; P < 0.05) and a reduction in connective tissue (52.2%, 27.92 ± 5.36 vs 13.34 ± 6.86%; P < 0.05). Statistical analysis was performed using Kolmogorov-Smirnov and homoscedasticity tests. For the muscle weight and muscle glycogen content, two-way ANOVA and the Tukey test were used. For the crosssectional area and connective tissue content, Kruskal-Wallis and Tukey tests were used. This study emphasizes the importance of anabolic pharmacological protection during immobilization to minimize skeletal muscle alterations resulting from disuse.

IGF-1 minimiza os efeitos deletérios do desuso no músculo sóleo de ratos

“…Muscle disuse provoked by conditions of lengthy confinement to bed, use of orthosis, fixation of limbs or microgravity induces the state of insulin resistance and consequently a catabolic state in the skeletal muscles. 5 To this effect, Ploug et al 11 refined the understanding of muscular metabolic behavior during a short period of immobilization (48 hours) in demonstrating significant decrease in the population of GLUT1 and GLUT4 transporters in the red fibers. The reduction in the number of insulin receptors and of the kinase activity of the receptor suggests, in a short period of time, resistance to glucose transport that is specific to the type of fiber and selective to the contractile process and to the action of insulin.…”

“…4 Aiming to minimize the events triggered by muscle disuse, various techniques have been used in an attempt to improve the homeostatic conditions of muscle fibers, with special emphasis on neuromuscular electrical stimulation, drugs such as clenbuterol and supplements such as vanadyl sulfate, creatine, glutamine and CGT (creatine, glutamine and taurine). 5 In literature, there are studies related to the signaling pathway whereby the mechanical stimulus and the activity of IGF-1 (growth factor similar to insulin 1) lead to functional changes in the satellite cells, quantity of muscle DNA, quantity of muscle protein, muscle mass and muscle fiber area. 6 According to Barton-Davis et al 7 , the local expression of IGF maintains muscle mass and strength during aging.…”

“…For immobilization, the rats were anesthetized (sodium pentobarbital, 40mg/Kg of body weight) and the acrylic resin orthosis was adapted with the ankle kept in neutral position (90˚). 5 IGF-1 (Sigma, code I2656) was administered subcutaneously in the daily dose of 50mg/Kg 9 . The period both of immobilization and of treatment was seven days.…”

“…The cross section areas of 375 soleus muscle fibers per animal were determined as follows: 15 fibers by area, with five areas by section, and five sections by animal. For the choice of fibers to be analyzed the participants used a reticle with squares measuring 12.100µm 2 in area, containing 20 straight line intersections, and t considered the fibers that coincided with 15 intersections in a random manner The intramuscular connective tissue area density analysis was quantified using the point counting planimetry system, 5 by means of a reticle with 2.500µm 2 squares containing 56 straight line intersections. Coincident points in the endomysium and perimysium were counted in five areas per section, with five sections per animal, totaling 1.400 points per animal.…”

Oral creatine supplementation attenuates muscle loss caused by limb immobilization: a systematic review

“…Creatine is a compound naturally present in meat and fish, normally obtained through diet and / or synthesized by the body using the amino acids arginine, glycine and methionine (12,13). On an omnivore diet, usually 1g of creatine ids ingested per day, half the daily requirement.…”