title: Stimulation of the Na+,K(+)-ATPase activity of K562 human erythroleukemia cells by triiodothyronine.
abstract: The effect of triiodothyronine (T3) on Na+,K(+)-ATPase activity of K562 human erythroleukemic cell was studied to understand why the erythrocyte sodium pump activity is decreased in hyperthyroidism. Na+,K(+)-ATPase activity of K562 cell lysates was assayed by measuring the release of inorganic phosphate (Pi) from ATP. Na+,K(+)-ATPase activity of K562 cell grown in the presence of T3 for 48 hours was significantly higher than that of control (0.98 +/- 0.05 mumol Pi h-1 mg protein-1 vs 0.82 +/- 0.10 mumol Pi h-1 mg protein-1, p < 0.05). The Na+,K(+)-ATPase activity could be stimulated in a time- and concentration-dependent manner; maximum stimulatory effect of T3 was seen at a concentration of 10(-7) mol/L. When an inducer [cytosine-beta-D-arabino-furanoside (ARA-C)] was added to the culture medium, the K562 cells showed signs of differentiation and synthesised haemoglobin. At the same time, the Na+,K(+)-ATPase activity remained high. We conclude that T3 stimulates Na+,K(+)-ATPase activity of K562 cells and in the presence of T3 during differentiation, the enzyme activity remains high.
authors.affiliation: Department of Chemical Pathology, Chinese University of Hong Kong, Shatin, N.T.
authors.forename: M
authors.initials: M
authors.lastname: Arumanayagam
authors.forename: R
authors.initials: R
authors.lastname: Swaminathan
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism; D015672:Erythroid Precursor Cells / Q000187:drug effects; D006801:Humans; D006980:Hyperthyroidism / Q000378:metabolism; D004915:Leukemia, Erythroblastic, Acute / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014284:Triiodothyronine / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D003561:Cytarabine; D014284:Triiodothyronine; D000254:Sodium-Potassium-Exchanging ATPase