Fiber-type-specific alpha B-crystallin distribution and its shifts with T-3 and PTU treatments in rat hindlimb muscles

Changes in alpha B-crystallin content in adult rat soleus and extensor digi torum longus (EDL) were examined after 8 wk of 3,5,3'-triiodothyronine (T-3 ) and propylthiouracil (PTU) treatments. Cellular distributions of alpha B- crystallin expression related to fiber type, and distribution shifts with t hese treatments were also examined in detail from the gray level of reactiv ity to specific anti-alpha B-crystallin antibody. alpha B-crystallin conten t in both soleus and EDL muscles was significantly decreased after T-3, and that in EDL was significantly increased over twofold after PTU treatment. In both control soleus and EDL muscles, the gray level of type I fibers was higher than that of type II fibers. alpha B-crystallin expression among ty pe II subtypes was muscle specific; the order was type I > IIa > IIx > IIb in control EDL muscle and type IIx greater than or equal to IIa in soleus m uscle. The relation was basically unchanged in both muscles after Ts treatm ent and was, in particular, well maintained in EDL muscle. Under hypothyroi dism conditions with PTU, the mean alpha B-crystallin levels of type IIa an d IIx fibers were significantly lower than levels under control conditions. Thus the relation between fiber type and the expression manner of stress p rotein alpha B-crystallin is muscle specific and also is well regulated und er thyroid hormone, especially in fast EDL muscle.