Effects of genistein on stereological and hormonal characteristics of the pituitary somatotrophs in rats.

The hypothalamic-pituitary somatotropic system plays a pivotal role in the regulation of physiological processes and metabolism, which is modulated by gonadal steroids. Considering that genistein belongs to the phytoestrogen family and acts via similar mechanisms to estrogens, the present study was designed to demonstrate whether genistein modulates the morphofunctional characteristic of somatotrophs [growth hormone (GH) cells] in adult rats in comparison with the effects of estradiol. In the study, the orchidectomized adult rats were used as an appropriate model system for testing the effects of this hormone-like substance. Changes in the pituitary somatotrophs were evaluated histologically and stereologically, while GH level was determined biochemically. Using immunolabelling and stereological methods, we showed that orchidectomy (Orx) provoked the decrease of GH cell volume density. After estradiol treatment of Orx rats, the most prominent change concerned the pituitary relative intensity of GH fluorescence and circulating GH level, which were elevated 77 % and 4.7-fold, respectively. Clearly, in contrast to orchidectomy, estradiol treatment enhanced the GH cells activity. Genistein treatment increased pituitary weight and volume, GH cell volume density, the total number of GH cells, and GH blood concentration (1.3-fold) in comparison to the Orx group. Although identical tendencies followed estradiol and genistein administration, the changes observed after genistein treatment were milder compared to estradiol treatment.