Fiber type composition of unoperated rat soleus and extensor digitorum longus muscles after unilateral isotransplantation of a foreign muscle in long-term experiments

We examined the effects of the unilateral heterochronousisotransplantation on the fiber type composition and myosinheavy chain (MyHC) isoform content of unoperated slow soleusand fast extensor digitorum longus muscles of female inbredLewis strain rats. Comparison was made between “control”unoperated muscles of experimental rats (after intramusculartransplantation surgery) with the corresponding muscles ofcompletely naive (unoperated) rats of three age groups (5-, 8-and 14-month-old). This was done in order to ascertain whetherthese muscles can be used as reliable controls to thetransplanted and host muscles for our ongoing graftingexperiments. The fiber type composition was determined byassessing the histochemical reaction for myofibrillar adenosinetriphosphatase, the MyHC isoform content was determinedimmunocytochemically using monoclonal antibodies specific todifferent MyHC isoforms and by sodium dodecyl sulphatepolyacrylamide gel electrophoresis. Our experiments show thatthe heterochronous intramuscular isotransplantation procedurehad no significant effect on the fiber type composition and MyHCisoform content of the “control” unoperated muscles of theexperimental rats when compared to the corresponding musclesof the naive animals. Furthermore, the duration and type ofisotransplantation did not also lead to differences amongcorresponding “control” muscles of experimental animals. Weconclude that the unoperated muscles of the experimental ratscan be used as controls in our current transplantation projectdealing with long-term grafting experiments.