Preferential uptake of estradiol in the pituitary and hypothalamus of mature male rats in the presence of testosterone

Simultaneous intravenous injection of 3H-estradiol and 14C-testosterone into adult male rats resulted in significant concentration of both labels in the blood and the diencephalon 2 h after the injection. In the pituitary-hypothalamic area only estradiol-derived radioactivity could be detected while testosterone-derived 14C label was not found. The results are interpreted to indicate that in males estradiol, not testosterone, may provide the homeostatic balance between the gonads and the hypothalamo-pituitary axis. (author)