Local action of intrahypophyseal implants of estrogen as revealed by staining with peroxidase-labeled antibody Supported in part by research grants from the USPHS (HD 03159-02) and from the University of Michigan Horace H. Rackham School of Graduate Studies.

Abstract

The direct action of 17 Β-estradiol and cholesterol on cells of the pituitary pars distalis, as revealed by staining with peroxidase-labeled antibody, was studied in female rats. Pellets of pure cholesterol and of estradiol mixed with cholesterol were implanted into the left lobe of the pars distalis 14–32 days after ovariectomy and left in place for 7–16 days. Rabbit antisera to rat prolactin, human growth hormone, human chorionic gonadotropin (for gonadotropes — presumably luteinizing hormone cells), and porcine corticotropin were used. In no case were cells altered in the contralateral lobe of the pars distalis; cholesterol likewise had no significant effect on the ipsilateral lobe. However, in the ipsilateral lobe containing an estrogen pellet, prolactin cells were hypertrophied and hyperplastic; cells assumed to be responsible for luteinizing hormone secretion were reduced in size and stained more intensely; and growth hormone cells were reduced in size. Corticotropin cells remained unaffected. For the most part estrogenic effects were distributed ventrally, caudally and laterally from the pellet and not far medially, never reaching the midline. It was concluded that estrogen acts directly on the hypophysis, the spread of the effects reflecting the direction of blood flow within the gland. These observations support the hypothesis that the pituitary gland serves as a site for feedback action by estrogen.