IN-SITU HYBRIDIZATION STUDY OF ESTROGEN-RECEPTOR MESSENGER-RIBONUCLEIC-ACID IN HUMAN ADENOHYPOPHYSEAL CELLS AND PITUITARY-ADENOMAS

Estrogen receptor (ER) was demonstrated in nontumorous and adenomatous human pituitaries by autoradiography and biochemical assays. In the p resent study, we investigated ER mRNA by in situ hybridization applied on paraffin section of 9 nontumorous pituitaries obtained at surgery or autopsy and 109 surgically removed adenomas. In nontumorous pituita ries, in situ hybridization combined with immunocytochemistry revealed hybridization signal in GH-, PRL-, ACTH-, TSH-, and LH/FSH-immunoreac tive cells, with the highest intensity in PRL-immunoreactive cells. ER mRNA was also localized in Crooke's cells, corticotrophs extending to posterior lobe, cells lining the pars intermedia cavities, and squamo us nests of pars tuberalis. The neurohypophysis, endothelium, and conn ective tissue expressed no ER gene. ER mRNA was present in all adenoma types, including somatotroph, lactotroph, mixed somatotroph-lactotrop h, mammosomatotroph, acidophil stem cell, functioning and silent corti cotroph, thyrotroph, gonadotroph, null cell adenomas, and oncocytomas. The strongest signal was seen in some lactotroph and mammosomatotroph adenomas. In 9 lactotroph adenomas exposed to bromocriptine (long-act ing repeatable injectable form), the hybridization signal was weak or absent, suggesting that suppression of ER gene plays a role in the inh ibition of PRL synthesis and tumor growth.