| Research Abstract |
It has been reported that the pituitary-specific transcriptional factor (Pit-1/GHF-1) gene produces nuclear binding protein composed of 291 amino acids (1). Semmons and colleagues (3) recently reportedthat in developing rat pituitary glands, Pit-1mRNA is distributed in all anterior cells, but that Pit-1 protein is expressed in certain cells (i.e., GH,PRL,TSH cells).
PRODUCTION OF ANTI-HUMAN (h) Pit-1 ANTIBODY AND IMMUNOHISTOCHEMISTRY
A 14 amino acid peptide KVRRIKLGYTQTNV was produced on a peptide synthesizer corresponding to the huamn Pit-1 amino acid sequence 149-162. Polyclonal antibody was raised againt the synthetic peptide in rabbits. The immunohisotchemical studies showed that many cells in the normal pituitary glands obtained at autopsy were positive for Pit-1 protein which was strictly localized in the nuclei. In serial sections, Pit-1 product was frequently localized in the nuclei of GH cells, PRL cells and somatomammotrophs (GH+PRL) (Fig.). The double staining method revealed
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that Pit-1 protein was localized in the nuclei of GH cells and PRL cells. These results may suggest the role of Pit-1 product in functional differentiation and maintenance of pituitary cells toward GH and PRL in physiologic condition.
IMMUNOHISTOCHEMICAL DETECTION OF hPit-1 PROTEIN IN THE HUMAN PITUITARY ADENOMAS
Among 86 patients studied immunohistochemically, a total of 38 adenomas were positive for Pit-1 product. In these 38 adenomas, Pit-1 product was specifically localized in the nuclei. All TSH ade-nomas were positive for Pit-1 product. 27 of 51 GH producing adenomas were positive.
IMMUNOHISTOCHEMICAL DETECTION OF Pit-1 PROTEIN IN THE PITUITARY ADENOMAS OF hGRF TRANGENIC MICE
It has been well documented that human GRF transgenic mice can develop pituitary hyperplasia andadnomas after about 10 months. The adenomas are well demarcated and are composed of larger and morechromophobic monotonous cells comparing to those acidophilic cells in the hyperplastic areas. The adnoma cells are immunohistochemically positive for GH,PRL and hGRF.alpha subunit, LHbeta, FSHbeta and ACTH are negative. Scattered and hypertrophic TSHbeta positive cells are also present in the adenomas. The presence of hypertrophic TSHbeta positive cells are considered to be a marker of the neoplastic transformation of hyperplastic cells. The adenomas are more prominently positive for Pit-1 protein in the nuclei comparing to the staining in the hyperplastic areas. These results suggest that Pit-1 protein may play a role in the functional differentiation in adenomatous cells in addition to the autocrine stimulation via GRF production. Less
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