title: Intracellular and plasma membrane-initiated pathways involved in the [Ca2+]i elevations induced by iodothyronines (T3 and T2) in pituitary GH3 cells.
abstract: The role of 3,5,3'-triiodo-l-thyronine (T3) and its metabolite 3,5-diiodo-l-thyronine (T2) in modulating the intracellular Ca(2+) concentration ([Ca(2+)](i)) and endogenous nitric oxide (NO) synthesis was evaluated in pituitary GH(3) cells in the absence or presence of extracellular Ca(2+). When applied in Ca(2+)-free solution, T2 and T3 increased [Ca(2+)](i), in a dose-dependent way, and NO levels. Inhibition of neuronal NO synthase by N(G)-nitro-l-arginine methyl ester and l-n(5)-(1-iminoethyl)ornithine hydrochloride significantly reduced the [Ca(2+)](i) increase induced by T2 and T3. However, while depletion of inositol trisphosphate-dependent Ca(2+) stores did not interfere with the T2- and T3-induced [Ca(2+)](i) increases, the inhibition of phosphatidylinositol 3-kinase by LY-294002 and the dominant negative form of Akt mutated at the ATP binding site prevented these effects. Furthermore, the mitochondrial protonophore carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone prevented the increases in both [Ca(2+)](i) and NO elicited by T2 or T3. Interestingly, rotenone blocked the early [Ca(2+)](i) increases elicited by T2 and T3, while antimycin prevented only that elicited by T3. Inhibition of mitochondrial Na(+)/Ca(2+) exchanger by CGP37157 significantly reduced the [Ca(2+)](i) increases induced by T2 and T3. In the presence of extracellular calcium (1.2 mM), under carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone, T2 and T3 increased both [Ca(2+)](i) and intracellular Na(+) concentration; nimodipine reduced the [Ca(2+)](i) increases elicited by T2 and T3, but inhibition of NO synthase and blockade of the Na(+)/H(+) pump by 5-(N-ethyl-N-isopropyl)amiloride prevented only that elicited by T3; and CB-DMB, bisindolylmaleimide, and LY-294002 (inhibitors of the Na(+)/Ca(2+) exchanger, PKC, and phosphatidylinositol 3-kinase, respectively) failed to modify the T2- and T3-induced effects. Collectively, the present results suggest that T2 and T3 exert short-term nongenomic effects on intracellular calcium and NO by modulating plasma membrane and mitochondrial pathways that differ between these iodothyronines.
authors.affiliation: Dipartimento di Scienze per la Biologia, la Geologia e l'Ambiente, Università del Sannio, Piazza Guerrazzi 1, Benevento, Italy.
authors.forename: Adelaide
authors.initials: A
authors.lastname: Del Viscovo
authors.forename: Agnese
authors.initials: A
authors.lastname: Secondo
authors.forename: Alba
authors.initials: A
authors.lastname: Esposito
authors.forename: Fernando
authors.initials: F
authors.lastname: Goglia
authors.forename: Maria
authors.initials: M
authors.lastname: Moreno
authors.forename: Lorella M T
authors.initials: LM
authors.lastname: Canzoniero
mesh_terms: D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D004104:Diiodothyronines / Q000494:pharmacology*; D019793:Fluorescein; D005456:Fluorescent Dyes; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D012964:Sodium / Q000378:metabolism; D014162:Transfection; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D002118:Calcium; D002352:Carrier Proteins; D004104:Diiodothyronines; D019793:Fluorescein; D005456:Fluorescent Dyes; D015544:Inositol 1,4,5-Trisphosphate; D007473:Ion Channels; D009569:Nitric Oxide; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D012964:Sodium; D014284:Triiodothyronine; C111205:4,5-diaminofluorescein; C030103:3,5-diiodothyronine