Soy Phytoestrogens Do Not Fully Reverse Changes in Rat Pituitary Castration Cells: Unbiased Stereological Study

Abstract

The aim of the study was to examine the potential of the principal soy isoflavones, genistein and daidzein, or isoflavone rich soy extract to recover pituitary castration cells in orchidectomized adult male rats in comparison with the effects of estradiol. Two weeks post orchidectomy (Orx), animals received estradiol‐dipropionate, genistein, daidzein or soy extract subcutaneously for 3 weeks. Control sham‐operated (So) and Orx rats received just the vehicle. Changes in the volumes of pars distalis, of individual follicle‐stimulating hormone (FSH) and luteinizing hormone (LH) containing cells, their volume, numerical density and number were determined by unbiased design‐based stereology. The intracellular content of βFSH and βLH was estimated by relative intensity of fluorescence (RIF). Orchidectomy increased all examined stereological parameters and RIF. Compared to Orx, estradiol increased the volume of pars distalis, but reversed RIF and all morphometric parameters of gonadotropes to the level of So rats, except their number. Treatments with purified isoflavones and soy extract decreased RIF to the control So level, expressing an estradiol‐like effect. However, the histological appearance and morphometrical features of gonadotropes did not follow this pattern. Genistein increased the volume of pars distalis, decreased the volume density of LH‐labeled cells and raised the number of gonadotropes. Daidzein decreased the cell volume of gonadotropic cells but increased their number and numerical density. Soy extract induced an increase in number and numerical density of FSH‐containing cells. Therefore, it can be concluded that soy phytoestrogens do not fully reverse the Orx‐induced changes in pituitary castration cells.