[Biochemical aspects of hormone-dependent muscles]

Different sensitivity of muscle fibres to hormones might be an important factor in regulating differing properties of individual muscles, in addition to the well known neural effects on muscle fibres. The peculiar sensitivity of rat perineal muscles to androgens is a striking example, whose relevance to function is self explanatory in muscles connected with the sexual apparatus. Besides these qualitative differences, quantitative differences too can be observed when the responses of different muscles to hormones active on glycogen are compared. Data concerning the effects of androgens, insulin and hydrocortisone on perineal and skeletal muscles (soleus, gastrocnemius, extensor digitorum longus, quadricipes, obliquus externus abdominis and diaphragm) support this statement. However, the physiological meanings of these differences remain obscure.