Pituitary specific transcription factor messenger ribonucleic expression in adenomatous and nontumorous human pituitary tissues.
BACKGROUND
The pituitary-specific transcription factor, Pit-1/GHF-1 (Pit-1) is a member of the POU family of homeobox genes. This transacting factor has a role in the development and expression of selected anterior pituitary cells including prolactin, growth hormone (GH), and thyrotropin, cell types in rodent pituitary. The expression of Pit-1 mRNA in human pituitaries has not been previously analyzed and the role of specific secretagogues in the regulation of Pit-1 transcripts in human pituitary adenomas has not been examined. Analysis of Pit-1 expression in normal and neoplastic human pituitaries may provide insight into the specificity of this transcription factor for pituitary cell types and the role of Pit-1 in human pituitary function.


METHODS
In situ and Northern hybridization analyses were used to study the expression of Pit-1 mRNA in surgically removed human pituitary adenomas and nontumorous pituitaries obtained within 6 hours postmortem. A cultured GH surgically removed adenoma was used to analyze the regulation of GH and Pit-1 in vitro.


RESULTS
In situ hybridization localized Pit-1 mRNA in all pituitary adenomas, although the mRNA levels in GH and prolactin adenomas were significantly higher than those in ACTH, null cell and gonadotroph tumors. Northern hybridization analysis revealed a 2.4 and a 1.2 kb mRNA transcript for Pit-1. Although GH mRNA transcript was markedly changed by dexamethasone and phorbol 12-myristate 13-acetate in vitro, Pit-1 mRNA transcripts were not changed significantly by these secretagogues.


CONCLUSIONS
Pit-1 mRNA transcripts are expressed mainly in prolactin and GH pituitary adenomas, but are also found in other adenomas and in the nontumorous adult human pituitary. Pit-1 mRNA transcript levels are not readily modulated in cultured GH adenoma cells by various secretagogues in vitro compared with the marked modulation of GH mRNA transcripts by these same secretagogues.
Lloyd
R V
RV
Department of Pathology and Surgery (Neurosurgery Section) University of Michigan, Ann Arbor.
Jin
L
L
Chandler
W F
WF
Horvath
E
E
Stefaneanu
L
L
Kovacs
K
K
D000236:Adenoma / Q000737:chemistry* / Q000473:pathology*; D000324:Adrenocorticotropic Hormone / Q000032:analysis / Q000235:genetics; D015152:Blotting, Northern; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D013006:Growth Hormone / Q000032:analysis / Q000235:genetics; D006801:Humans; D017403:In Situ Hybridization; D010902:Pituitary Gland / Q000737:chemistry* / Q000166:cytology* / Q000473:pathology; D010911:Pituitary Neoplasms / Q000737:chemistry* / Q000473:pathology*; D011388:Prolactin / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis* / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013972:Thyrotropin / Q000032:analysis / Q000235:genetics; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured / Q000473:pathology
D004268:DNA-Binding Proteins; C494187:POU1F1 protein, human; D012333:RNA, Messenger; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D013972:Thyrotropin; D013006:Growth Hormone; D013755:Tetradecanoylphorbol Acetate; D004121:Dimethyl Sulfoxide