title: Effect of P1-purinergic agonist on thyrotropin stimulation of H2O2 generation in FRTL-5 and porcine thyroid cells.
abstract: Our previous studies have shown that the generation of H2O2 in FRTL-5 thyroid cells is regulated via both the adenylate cyclase/cyclic adenosine monophosphate (cAMP) and Ca2+/phosphatidylinositol pathway: thyrotropin (TSH) stimulates H2O2 generation through both pathways, via the former at a low concentration and via the latter at a high concentration. In porcine thyrocytes in primary culture H2O2 generation is stimulated only via the Ca2+/phosphatidylinositol route. In the present study we explored the effect of a P1-purinergic agonist (phenylisopropyladenosine, PIA) on stimulations induced by TSH and by adenosine triphosphate (ATP), an activator of the Ca2+/phosphatidylinositol cascade via the P2-purinergic receptor. In FRTL-5 cells, PIA potentiated H2O2 generation stimulated by TSH at 10 U/l (but not at 1 U/l, Ca2+ mobilization induced by TSH and Ca2+ mobilization induced by ATP at 1 mumol/l (but not 10 mumol/l). Phenylisopropyladenosine strongly inhibited TSH-induced cAMP accumulation in FRTL-5 cells. In pig thyrocytes, PIA had no effect on H2O2 generation stimulated by TSH or ATP and no effect on ATP-stimulated Ca2+ mobilization. Also, PIA did not inhibit TSH-stimulated cAMP accumulation in pig thyrocytes, and by itself had no effect on H2O2 generation or Ca2+ mobilization. Thus, in FRTL-5 cells, but not in porcine thyrocytes, PIA modulates TSH-stimulated H2O2 generation by enhancing the Ca2+/phosphatidylinositol route and inhibiting the adenylate cyclase/cAMP route of the TSH signal. The net result of this modulation apparently depends on the balance between inhibition of the cAMP route and enhancement of the Ca2+ route. This may explain the lack of potentiation observed by 1 U/l TSH.
authors.affiliation: Department of Anatomy, University of Göteborg, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Björkman
authors.forename: R
authors.initials: R
authors.lastname: Ekholm
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D003470:Culture Media; D000242:Cyclic AMP / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D010660:Phenylisopropyladenosine / Q000494:pharmacology*; D051381:Rats; D013552:Swine; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000502:physiology*
chemical_list: D003470:Culture Media; D010660:Phenylisopropyladenosine; D000255:Adenosine Triphosphate; D013972:Thyrotropin; D006861:Hydrogen Peroxide; D000242:Cyclic AMP; D002118:Calcium