THE EFFECT OF ANTERIOR PITUITARY HORMONES ON EXPERIMENTALLY INDUCED MUSCULAR ATROPHY AND ON TIBIAL EPIPHYSIAL CARTILAGE WIDTH IN NORMAL AND HYPOPHYSECTOMIZED RATS.

Abstract

SUMMARY 1. Unilateral section of the sciatic nerve causes atrophy of the gastrocnemius muscle with consequent reduction in wet weight and in fibre size of the muscle in both hypophysectomized and non-hypophysectomized animals. 2. The administration of growth hormone, thyroid-stimulating hormone (TSH), follicle-stimulating, luteinizing and adrenocorticotrophic hormone, either before nerve section, immediately after nerve section or some time after atrophy has been established, had no effect on muscle fibre size. 3. The administration of TSH during the period immediately following nerve section caused a significant reduction in the tibial epiphysial cartilage width of the denervated limb. No difference in cartilage width between denervated and innervated limbs was observed following treatment with any of the other hormones. 4. In both normal and hypophysectomized animals the effect of the hormones on body weight and on the weight of normal and atrophic muscles was in keeping with their known physiological actions. 5. It is concluded that anterior pituitary hormones act on muscles by virtue of their well-known anabolic or catabolic properties, that their effects on total body weight and innervated and denervated muscle are generally similar and that, under the experimental conditions used, none of the hormones studied was capable of preventing the occurrence of atrophy in denervated muscle.