Estrogen target cells in the pituitary of platyfish,Xiphophorus maculatus

Summary The distribution of estradiol-concentrating cells in the pituitary of the platyfish, Xiphophorus maculatus, is studied after the injection of ³H estradiol-17 by thaw-mount autoradiography. Autoradiograms prepared 2–8 h after the injection show nuclear concentration of radioactivity in certain cells of the proximal pars distalis, while no nuclear labeling is found in 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.Supported by PHS grant NS09914. The authors are grateful to Dr. D.G. Humm for providing the platyfish