[Effect of gravitation loading and retabolil on development of atrophy in muscles and bones of rats due to suspension].

In a 3-wk experiment with tail-suspended rats histological and histomorphometric methods were used to determine the effects of graded gravitational loading (GGL) and anabolic steroid retabolil (nortestosterone decanoate) on the course of atrophy in soleus m. (SM), gastrocnemius m. (GM), tibia and humerus, and functioning of somatotrophic hormones (STH) of the pituitary and thyrocytes of the thyroid. Suspension was found to produce atrophy in SM and, to a less degree, in GM, partial transformation of SM slow fibers into the fast ones, suppression of the tibial longitudinal growth, demineralization of the tibial and humeral spongious metaphyses; besides, functional activities of STH-cells and thyrocytes were inhibited. Graded gravitational loading of rats by intermittence of suspension for 2 hrs slowed down atrophy in both muscles and osteopenia in tibia, stimulated the synthetic and secretory functions of STH-cells without any marked effect on thyrocytes or humeral osteopenia. GGL failed to influence the slow-to-fast transformation of SM fibers. Two injections of retabolil at the total dose of 3 mg/kg of the body mass somewhat interfered with the SM atrophy and humoral osteopenia, and were favorable to the synthetic but not secretory activity of STH-cells. Neither SM and tibial atrophies nor thyroid activity of the gland were improved. The prophylactic action of GGL upon the SM and humeral atrophies was significantly higher when combined with retabolil, whereas GM and tibia were not noticeably cured by retabolil. Inhibition of the SM atrophy and humeral osteopenia in rats treated with GGL and retabolil concurred with elevated activities of STH-cells and thyrocytes indirectly suggesting their more intensive production of the growth hormone and thyroid hormones, respectively.