title: Thyroid hormones and active calcium transport of inside-out red cell membrane vesicles.
abstract: Thyroid hormones may influence the active transport of Ca2+ across the cell membrane. To test the physiologic relevance of this mechanism, we used inside-out human red cell membrane vesicles as a model of the cell membrane Ca2+ pump. We monitored by spectrophotometric methods the kinetics of the uptake of Ca2+ in the presence of 10(-5)-10(-10) M thyroid hormones or their analogues. Vesicles freed of calmodulin and protein inhibitor(s) of the Ca2+ pump were also obtained. The results are as follows: (1) Thyroxine inhibits the active Ca2+ uptake; (2) this effect antagonizes that of soluble calmodulin; and (3) triiodothyronine and other analogues of the thyroid hormones are less active than thyroxine. We conclude that the thyroid hormones may influence cell Ca2+ homeostasis by direct action on the Ca2+ pump.
authors.affiliation: Sezione Fisiopatologia dell'Osso e del Metabolismo Minerale, Università di Milano, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Rubinacci
authors.forename: P
authors.initials: P
authors.lastname: Divieti
authors.forename: S
authors.initials: S
authors.lastname: Lodigiani
authors.forename: A
authors.initials: A
authors.lastname: De Ponti
authors.forename: M
authors.initials: M
authors.lastname: Samaja
mesh_terms: D000328:Adult; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000097:blood*; D000252:Calcium-Transporting ATPases / Q000187:drug effects; D002147:Calmodulin / Q000037:antagonists & inhibitors; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D013963:Thyroid Hormones / Q000494:pharmacology*; D013974:Thyroxine / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D013963:Thyroid Hormones; D014284:Triiodothyronine; D000252:Calcium-Transporting ATPases; D013974:Thyroxine; D002118:Calcium