Endocrine Abstracts

Daidzein, one of the main phytoestrogens of soy, is able to act as estrogen-like compounds due to its structural similarity with 17β-estradiol, which gives them the capacity to bind estrogen receptors and to induce hormone-like effects. Considering, that somatotropic system is sensitive to sex steroids, the aim of this study was to investigate the effects of daidzein on stereological and biochemical parameters of pituitary somatotropic (GH) cells in orchidectomized adult rat. Adult Wistar rat were divided into two groups: orchidectomized rat s.c. treated with medium (absolute etanol and sterile olive oil mixture; Orx) and orchidectomized rats s.c. treated with daidzein in medium (30 mg/kg BW; Orx+D). The groups of animals received the treatment during three weeks and were sacrificed 24 h after the last injected dose. Immunohisochemically labeled pituitary section were stereologically analysed, using NewCast Stereological Software Package. The circulating GH was determined biochemically. The volume density of pituitary GH cells was increase (P<0.05) after daidzein treatment (25.6±2.4%), in comparation to Orx group (20.1±1.15%). In addition, intensity of staining of GH cell and volume of GH cells were increased (P<0.05) after daidzein treatment (2172.6±110.8 μm³), in comparision with Orx group (1203.8±174.9 μm³) as well. Numerical density and absolute number of GH cells were decrease (P<0.05) after daidzein treatment (10.8±0.6×10⁴ mm⁻³; 5.6±0.8×10⁵ respectively), in comparison to Orx group (16.8±2.1×10⁴ mm⁻³; 7.6±0.9×10⁵). The treatment did not affect GH level in blood. These results indicated that daidzein has provoked diferent changes of the stereological parameters of GH cells, which did not affect GH blood level. It can be concluded that response of somatotropic system to daidzein treatment includes, beside regulation at the level of the pituitary gland, other mechanisms of regulation of GH secretion.