Comparison of effect of oestrogen on muscle development of male and female mice.

The effect of oestrogen on muscle development was determined in 8 muscles (biceps brachii, triceps brachii, common digital extensor, soleus, superficial digital flexor, cranial tibialis, gastrocnemius and long digital extensor muscles of sexually immature male and female mice. Each mouse was killed at a mature age of 16 weeks. The muscle development as determined by increase in muscle weight was significantly smaller in muscles of oestrogen-treated male and oestrogen-treated female mice as compared to the muscles of normal male and normal female mice. The muscles of normal male mice were very significantly larger than those of normal female mice. There was, on the other hand, no significant difference between the muscle mass of oestrogen-treated male and oestrogen-treated female mice. This indicated that the smaller mass of normal female mice when compared to normal male mice was connected with inhibitory effect of oestrogen on the muscle development of female mice.