Effects of a tryptophan deficient diet on the morphology of skeletal muscle fibers of the rat. Preliminary observations at neuroendocrinological and submicroscopical levels

It is proposed an animal model consisting of young male, L-tryptophan-deprived, namely 5-HT-free rats since their ontogenesis. This was obtained by feeding their mothers with a L-tryptophan-free (tf) diet since the day 1 of pregnancy. They were studied and compared with control rats of the same ages fed with a complete diet. Already at birth tf-litters were significantly underdeveloped as compared to the control newborn rats. Postnatal growth was in the tf-rats so poor that it worsened into a stricking dwarfism characterized by physical immaturity, muscular hypotrophy with alterations of motor activity and impairment of the hypothalamo-pituitary-axis. A radioimmunological study of growth hormone (GH) showed in tf-rats dramatic low plasma levels of the hormone, thus confirming the existence of serotonergic hypothalamo-pituitary pathways for GH in normal animals. By histological and ultrastructural examinations, hypotrophy and degenerative alterations of the muscle fibers could be observed. The possible causes for this finding are extensively considered and discussed.