Decreased TRH receptor mRNA activity precedes homologous downregulation: assay in oocytes.
Ligand-induced decrease in cell-surface receptor number (homologous downregulation) is often due to rapid receptor internalization. Thyrotropin-releasing hormone (TRH), however, causes a slow downregulation of TRH receptors (TRH-Rs), with a half-time of approximately 12 hours, in GH3 rat pituitary cells. The mechanism of TRH-R downregulation was studied by monitoring TRH-evoked depolarizing currents in Xenopus oocytes injected with GH3 cell RNA as a bioassay for TRH-R messenger RNA (mRNA) activity. In GH3 cells, TRH caused a rapid decrease in TRH-R mRNA activity to 15 percent of control within 3 hours. Because the half-life of TRH-R mRNA activity in control cells was approximately 3 hours, the rapid decrease in mRNA activity was not due to inhibition of mRNA synthesis alone and may represent a post-transcriptional effect.
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Department of Medicine, Cornell University Medical College, New York, NY 10021.
Straub
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Traktman
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Gershengorn
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D000818:Animals; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D008564:Membrane Potentials; D009363:Neoplasm Proteins / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000473:pathology; D012333:RNA, Messenger / Q000096:biosynthesis*; D012334:RNA, Neoplasm / Q000096:biosynthesis; D051381:Rats; D017981:Receptors, Neurotransmitter / Q000235:genetics / Q000378:metabolism*; D018025:Receptors, Thyrotropin-Releasing Hormone; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000378:metabolism; D014982:Xenopus laevis
D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D017981:Receptors, Neurotransmitter; D018025:Receptors, Thyrotropin-Releasing Hormone; D013973:Thyrotropin-Releasing Hormone