Thyrotropin-releasing hormone (TRH) gene expression in the anterior pituitary. I. Presence of pro-TRH messenger ribonucleic acid and pro-TRH-derived peptide in a subpopulation of somatotrophs.
We have previously reported the presence of authentic pro-TRH-derived peptides in cultured anterior pituitary (AP) cells. The present studies were undertaken to determine whether pro-TRH mRNA could be demonstrated in the AP and to elucidate the cell type expressing pro-TRH. AP cells were cultured for up to 18 days, during which time the content of both TRH and prepro-TRH-(25-50) rose significantly (P < 0.01). In contrast, the cellular contents of LH, FSH, TSH, and ACTH fell significantly (P < 0.01), whereas that of GH increased by 45.9% (P < 0.05). Northern blot analysis revealed that the levels of pro-TRH mRNA extracted from AP cells (18 days in culture) were similar to those in hypothalamic tissue from adult male rats, indicating a high relative abundance of this mRNA in the AP. In situ hybridization experiments showed a dense accumulation of silver grains over a subpopulation of cultured AP cells. A combination of in situ hybridization for pro-TRH mRNA and immunocytochemistry for pituitary hormones revealed colocalization of pro-TRH mRNA and GH in a subpopulation of somatotrophs. No colocalization with LH-, TSH-, PRL-, or beta-endorphin-containing cells was observed. Immunocytochemistry at the electron microscopic level demonstrated that prepro-TRH-(25-50) was contained in a subpopulation of secretory granules in AP cells expressing this pro-TRH-derived sequence. These studies demonstrate that pro-TRH mRNA is present in cultured AP cells in high concentration and that the pro-TRH gene is expressed within a subpopulation of somatotrophs.
Bruhn
T O
TO
Department of Medicine, Brown University/Rhode Island Hospital, Providence 02903.
Rondeel
J M
JM
Bolduc
T G
TG
Jackson
I M
IM
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D016375:Antisense Elements (Genetics); D001921:Brain / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D015870:Gene Expression; D017403:In Situ Hybridization; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D008854:Microscopy, Electron; D009928:Organ Specificity; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D011498:Protein Precursors / Q000096:biosynthesis*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism*; D051381:Rats; D013972:Thyrotropin / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000096:biosynthesis*; D014162:Transfection
D016375:Antisense Elements (Genetics); D011498:Protein Precursors; D012333:RNA, Messenger; C063596:prepro-thyrotropin-releasing hormone; D013973:Thyrotropin-Releasing Hormone; D000324:Adrenocorticotropic Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin; C046418:pro-thyrotropin releasing hormone; D011761:Pyrrolidonecarboxylic Acid