Background and aims: The aim of this study was to ascertain whether there are gender-related differences in the morphological characteristics of the soleus and tibialis anterior muscles in young adult and old Fischer 344/Brown Norway F1 rats. Methods: We tested 1) whether there was a gender-related difference between the fiber type composition of these muscles, and 2) whether the cross-sectional area of individual muscle fibers demonstrated gender-associated differences, fibers from males being larger than fibers from females. Results: Gender differences were not found in the fiber type composition of the soleus and tibialis anterior muscles, but were present in the single skeletal fiber cross-sectional area of the tibialis anterior muscle. The cross-sectional area of type I fibers in females was greater than that in males at both 12 (16%) and 30 (5%) months of age. In contrast, the cross-sectional area of type IIa fibers of 12-month-old males was larger than that of 12-month-old females. No significant differences between genders were found for the cross-sectional area of type IIb fibers in either age group. In the soleus muscle, 30-month-old males had larger single fiber cross-sectional areas of both fiber types I and IIa. At 12 months of age, type I fibers from females were larger than those from males. Conclusions: Our findings indicate that gender-related differences exist in the size of individual skeletal fibers from the soleus and tibialis anterior muscles and that they may influence metabolism and the adaptive response to rehabilitation programs.
- Aging rats
- Muscle fiber-type composition
- Skeletal muscles