Estrogen target cells in the pituitary of platyfish, Xiphophorus maculatus

The distribution of estradiol-concentrating cells in the pituitary of the platyfish, Xiphophorus maculatus, is studied after the injection of 3H estradiol-17 beta by thaw-mount autoradiography. Autoradiograms prepared 2-8 h after the injection show nuclear concentration of radioactivity in certain cells of the rostral pars distalis, pars intermedia and pars nervosa. Radioactively labeled cells are identified as gonadotropes by a combined technique of thaw-mount autoradiography and immunoperoxidase staining with antiserum to ovine LH. Approximately 80% of the immunoreactive LH cells show a concentration of radioactivity in their nuclei. These observations indicate that in teleosts, as in mammals, estradiol has a direct effect on pituitary gonadotropes.