REMODELING OF THE CYTOSKELETAL LATTICE IN DENERVATED SKELETAL-MUSCLE

The effect of denervation-induced atrophy on the cytoskeletal lattice in rat fast- and slow-twitch skeletal muscle has been investigated. Im munochemical analyses and immunofluorescence microscopy experiments em ploying monospecific antibodies to dystrophin, desmin, and a-tubulin w ere carried out on intact and denervated muscles. The relative cellula r content of dystrophin and desmin were reduced in the soleus muscle ( slow-twitch), while significant increases were shown in the gastrocnem ius muscle (fast-twitch). In both muscles, alpha-tubulin levels increa sed up to 12-fold as a function of time compared to control values. Im munofluorescence microscopy revealed a distinct rearrangement of the m icrotubule network toward a predominantly longitudinal alignment, whic h was accompanied by an increase in the density of the fluorescence. I t is concluded that the relative increase of the three structural prot eins in the fast-twitch gastrocnemius muscle may be related to the app arent resistance of this muscle type to denervation-induced atrophy. T he increased alpha-tubulin content in denervated slow- and fast-twitch muscles could be indicative of an adaptive mechanism designed to main tain the integrity of the muscle fiber in view of eventual regenerativ e activities. (C) 1996 John Wiley & Sons, Inc.