title: Effects of triiodothyronine administration on the adenylyl cyclase system in brown adipose tissue of rat.
abstract: This study was undertaken to investigate the effect of triiodothyronine (T3) administration to euthyroid rats on beta 3-adrenoceptor (beta 3-AR) expression and on the different components of the adenylyl cyclase (AC) system in brown adipose tissue (BAT). In rats treated with T3, the beta 3-AR density (assessed by the binding of [3H]CGP-12177) showed a decrease of 50%, as did their mRNA, as analyzed by reverse transcriptase-polymerase chain reaction. In hyperthyroid rats, compared with control rats, there was a 40% increase in G alpha s activity (stimulated by NaF or GTP gamma S) and a fourfold increase in the protein concentration (Western blotting). In contrast, the level of the pertussis toxin substrate Gi declined by 35% in response to T3. Analysis of dose-response curves for isoproterenol and CGP-12177 revealed that neither basal nor stimulated AC activities nor 50% stimulatory concentration for these agonists was changed by T3 administration. In conclusion, these results suggest that downregulation of the beta 3-AR by T3 was counter-balanced by changes in other components of the AC cascade (i.e., Gs and Gi), so no change occurred in the capacity of BAT to generate adenosine 3',5'-cyclic monophosphate.
authors.affiliation: Laboratoire de Pharmacologie Clinique et Expérixentale, Faculté de Médecine, Université Paris Nord, Bobigny, France.
authors.forename: H
authors.initials: H
authors.lastname: Adli
authors.forename: R
authors.initials: R
authors.lastname: Bazin
authors.forename: R
authors.initials: R
authors.lastname: Vassy
authors.forename: G Y
authors.initials: GY
authors.lastname: Perret
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D002001:Adipose Tissue, Brown / Q000201:enzymology*; D000318:Adrenergic beta-Agonists / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D015536:Down-Regulation; D019204:GTP-Binding Proteins / Q000378:metabolism; D006980:Hyperthyroidism / Q000378:metabolism; D008297:Male; D011412:Propanolamines / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012016:Reference Values; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D000318:Adrenergic beta-Agonists; D011412:Propanolamines; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D014284:Triiodothyronine; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; C033394:CGP 12177