RESUMO
Daidzein is a potential natural alternative to estradiol during therapy of some malignancies in men. Besides weak inhibition of tyrosine kinase activity, daidzein has a sizeable inhibitory effect on calcium channels. The aim of this study was to examine the effects of daidzein on the immunohistomorphometric features of pituitary adrenocorticotropes (ACTH cells) and circulating levels of ACTH and corticosterone, in comparison with estradiol, in an animal model of the andropause. Sixteen-month-old Wistar rats were divided into sham operated (SO), orchidectomized (Orx), estradiol treated orchidectomized (Orx+E) and daidzein treated orchidectomized (Orx+D) groups. Estradiol (0.625 mg/kg/day) and daidzein (30 mg/kg/day) were administered subcutaneously for three weeks, while the SO and Orx groups received the vehicle alone. ACTH cells were identified by the peroxidase-antiperoxidase (PAP) immunohistochemical procedure. Peripheral circulating concentrations of ACTH and corticosterone were measured by immunoassay. Orchidectomy reduced (p<0.05) the cell volume and volume density of adrenocorticotropes by 11% and 16%, respectively, in comparison to SO rats. In Orx+E rats, the volume density of ACTH cells decreased (p<0.05) by 25%, but the circulating level of ACTH increased (p<0.05) by 29%, compared to Orx rats. Daidzein treatment significantly decreased (p<0.05): volume density of ACTH cells, circulating ACTH and corticosterone by 24%, 48% and 33%, respectively, compared to the Orx group. In conclusion, this study revealed that daidzein negatively modulated the immunohistomorphometric features of ACTH cells and, unlike estradiol, decreased ACTH and corticosterone secretion, in an animal model of the andropause.