title: Thyroid hormone up-regulates thyroid hormone receptor beta gene expression in rat cerebral hemisphere astrocyte cultures.
abstract: Oligonucleotide probes complementary to specific regions of three thyroid receptor cDNAs were used to study the effects of thyroid hormone on the expression of the mRNAs encoding two alpha (alpha 1 and alpha 2) and one beta-thyroid (beta 1) receptors isoforms in rat cerebral hemisphere astrocyte cultures. Both genes are expressed by type 1 astrocytes. The levels of the alpha 1-, alpha 2-, and beta 1-mRNAs did not significantly change between day 8 and day 22, in cultures grown in the absence of thyroid hormone. L-triiodothyronine (L-T3) treatment of the cultures increased the levels of beta 1-mRNAs by fivefold without changing either the levels of the alpha 1- and alpha 2-mRNAs or L-T3 binding capacity. The effect of L-T3 on beta 1-mRNAs was observed after 4 h of treatment and was independent of protein synthesis, suggesting that this effect is likely to be a direct one. Treatment of the cultures by cytosine arabinosine, a drug that kills dividing cells, specifically decreased level of the alpha 1- and alpha 2-mRNAs by 60% and 38%, respectively. Finally, by immunocytochemistry, we showed that the beta 1 receptor-immunoreactivity was either located in the perinuclear region and the cytoplasm or in the nuclei of astrocytes. Taken together with previous data obtained in neuronal cultures where no effect of L-T3 was observed on the levels of the beta 1-mRNAs, our findings indicate that the beta 1 gene is differentially regulated in neurons and astrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Ontogenesis and Molecular Genetics, CHUL Research Center, Ste-Foy, Québec, Canada.
authors.forename: J M
authors.initials: JM
authors.lastname: Lebel
authors.forename: S
authors.initials: S
authors.lastname: L'Hérault
authors.forename: J H
authors.initials: JH
authors.lastname: Dussault
authors.forename: J
authors.initials: J
authors.lastname: Puymirat
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000502:physiology; D001921:Brain / Q000378:metabolism* / Q000502:physiology; D002478:Cells, Cultured; D015870:Gene Expression / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011988:Receptors, Thyroid Hormone / Q000235:genetics* / Q000378:metabolism; D013963:Thyroid Hormones / Q000494:pharmacology*; D014284:Triiodothyronine / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D012333:RNA, Messenger; D011988:Receptors, Thyroid Hormone; D013963:Thyroid Hormones; D014284:Triiodothyronine