Katoch Surender S, Garg Asha, Sharma Sushma
Department of Biosciences, Himachal Pradesh University, Summer Hill, Shimla 171 005, India.
Indian J Exp Biol. 2006 Jun;44(6):448-58.
The aim of this study was to determine the contribution of beta-adrenoceptor activation in the reconstruction of the structural and functional organization of denervated skeletal muscle. beta-agonists, clenbuterol (1.2 mg/kg body weight) and isoproterenol (2 mg/kg body weight), administration (daily oral administration; maximum 7 days) to normal innervated rats as well as denervated animals caused muscle hypertrophy. An increase in mean fiber diameter confirmed this stimulated growth both in normal innervated and denervated rat gastrocnemius muscle. Examination of muscle nuclei from treated but normal innervated rat gastrocnemius exhibited features like large size, active nucleoplasm and an increase in their number per fiber cross section and per mm mean fiber length indicating towards an elevated biosynthetic activity in tissue in the presence of beta adrenoceptor agonists. Administration of drugs to normal innervated animals resulted in an emergence of central muscle nuclei. The hyperactive and enlarged muscle nuclei ultimately organized themselves into unusually elongated nuclear streaks. beta agonist treatment to denervated rats resulted in amelioration of atrophic state of tissue characterized by hypertrophy of muscle fibers thus lending to a restoration of structural organization of tissue. Bizarre shapes of nuclei in denervated muscle tend to recover to that characteristic to normal innervated muscle in presence of clenbuterol and isoproterenol hydrochloride. All observations were confirmed by administering butoxamine, a beta-adrenoceptor antagonist along with beta-agonists. The results suggests that both clenbuterol and isoproterenol hydrochloride are capable of mimicking normal innervation functions in skeletal muscle and thus play important role in the structural and functional reorganization of tissue. Amelioration of denervation atrophy in rat gastrocnemius in the presence of beta-agonists supports this.
本研究的目的是确定β-肾上腺素能受体激活在失神经支配骨骼肌结构和功能组织重建中的作用。向正常神经支配的大鼠以及失神经支配的动物给予β-激动剂克伦特罗（1.2毫克/千克体重）和异丙肾上腺素（2毫克/千克体重）（每日口服给药；最长7天）会导致肌肉肥大。平均纤维直径的增加证实了正常神经支配和失神经支配的大鼠腓肠肌中这种刺激生长的情况。对经处理但正常神经支配的大鼠腓肠肌的肌核检查显示出一些特征，如体积大、核质活跃以及每纤维横截面积和每毫米平均纤维长度中核数量的增加，这表明在存在β-肾上腺素能受体激动剂时组织中的生物合成活性升高。向正常神经支配的动物给药导致中央肌核出现。活跃且增大的肌核最终组织成异常细长的核条纹。对失神经支配的大鼠进行β-激动剂治疗导致以肌纤维肥大为特征的组织萎缩状态得到改善，从而有助于恢复组织的结构组织。在克伦特罗和盐酸异丙肾上腺素存在的情况下，失神经支配肌肉中奇异形状的核倾向于恢复到正常神经支配肌肉的特征形状。所有观察结果都通过与β-激动剂一起给予β-肾上腺素能受体拮抗剂布托沙明得到了证实。结果表明，克伦特罗和盐酸异丙肾上腺素都能够模拟骨骼肌中的正常神经支配功能，因此在组织的结构和功能重组中发挥重要作用。β-激动剂存在时大鼠腓肠肌失神经支配萎缩的改善支持了这一点。
