Disorganization of honey-comb immunoreactive pattern of desmin and plectin in rat atrophic soleus muscle fiber induced by hindlimb suspension

Abstract

Immunoreactivity for desmin, plectin and a- actinin was inve s t i gated in rat atrophic soleus muscle fibers induced by hindlimb suspension between 1 and 4 weeks (hindlimb suspension group, HSG), and compared with that of the control group (CG). Some of the HSG for 4 weeks were allowed unrestricted cage activity for 2 weeks as the recovery group (RG). In the cross-sectioned muscle fibers of the CG, desmin and plectin show e d h o n ey-comb immunoreactive patterns ex t e n d i n g throughout the sarcoplasm. Superimposed images by double immunofluorescence labeling show e d overlapping of both immunoreactivities. In the longitudinally sectioned profiles, superimposed images of a-actinin and desmin were overlapped at the level of Z-discs. The focal disorganization of the above honey - comb immunoreactive patterns, followed by the reduction of the cross-sectional area (CSA) of atrophic soleus muscle fibers and the appearance of Z-streaming, uniquely arose in the HSG from the first week and extended throughout the sarcoplasm in proportion to the suspension period. Such honey-comb patterns of both desmin and plectin were already restored in the RG at 2 weeks, followed by the disappearance of Z-streaming, prior to the recovery of the CSA. These findings indicate that the disorganization of topological and structural relationships of desmin and plectin with Z-discs surrounding individual myofibrils is primarily evo ke d , which leads to Z-streaming of atrophic soleus muscle fibers, and that the restoration of the muscle activity results in an early arrangement recovery of desmin and plectin around myofibrils.