Effect of salbutamol on innervated and denervated rat soleus muscle.
The objective of the present investigation was to perform a 14-day time-course study of treatment with salbutamol, a beta2 adrenoceptor agonist, on rat soleus muscle in order to assess fiber type selectivity in the hypertrophic response and fiber type composition. Male Wistar rats were divided into four groups: control (N = 10), treated with salbutamol (N = 30), denervated (N = 30), and treated with salbutamol after denervation (N = 30). Salbutamol was injected intraperitoneally in the rats of the 2nd and 4th groups at a concentration of 0.3 mg/kg twice a day for 2 weeks. The muscles were denervated using the crush method with pean. The animals were sacrificed 3, 6, 9, 12, and 14 days after treatment. Frozen cross-sections of soleus muscle were stained for myosin ATPase, pH 9.4. Cross-sectional area and percent of muscle fibers were analyzed morphometrically by computerized image analysis. Treatment with salbutamol induced hypertrophy of all fiber types and a higher percentage of type II fibers (21%) in the healthy rat soleus muscle. Denervation caused marked atrophy of all fibers and conversion from type I to type II muscle fibers. Denervated muscles treated with salbutamol showed a significantly larger cross-sectional area of type I muscle fibers, 28.2% compared to the denervated untreated muscle. Moreover, the number of type I fibers was increased. These results indicate that administration of salbutamol is able to induce changes in cross-sectional area and fiber type distribution in the early phase of treatment. Since denervation-induced atrophy and conversion from type I to type II fibers were improved by salbutamol treatment we propose that salbutamol, like other beta2 adrenoceptor agonists, may have a therapeutic potential in improving the condition of skeletal muscle after denervation.
Soić-Vranić
T
T
Department of Anatomy, Medical Faculty, University of Rijeka, Braće Branchetta 20, 51000 Rijeka, Croatia. tamaras@medri.hr
Bobinac
D
D
Bajek
S
S
Jerković
R
R
Malnar-Dragojević
D
D
Nikolić
M
M
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000420:Albuterol / Q000494:pharmacology*; D000818:Animals; D008297:Male; D009121:Muscle Denervation; D018485:Muscle Fibers, Skeletal / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000294:innervation; D009133:Muscular Atrophy; D051381:Rats; D017208:Rats, Wistar
D000318:Adrenergic beta-Agonists; D000420:Albuterol