title: Effects of calcium on Na+,K(+)-ATPase isolated from human placenta.
abstract: It has been reported that Ca2+ can be either stimulatory or inhibitory of the activity of Na+,K(+)-ATPase obtained from different sources. The aim of the present work was to study the effect of increasing concentrations of Ca2+ on Na+,K(+)-ATPase activity and of placenta. The temperature dependence of Na+,K(+)-ATPase activity and of spectral parameters of a spin label paramagnetic maleimide) were also (MSL, 2,2,6,6-tetramethylpiperidin-1-oxyl-4-maleimide) were also investigated in absence and in presence of 2 mM Ca2+. Ca2+ affects positively the enzymatic activity and this effect is evident at all temperature tested. Maleimide spectral parameters are not affected by the presence of 2 mM Ca2+, showing that the microenvironments of SH groups are not modified following ion interactions.
authors.affiliation: Istituto di Biochimica, Facoltà di Medicina e Chirurgia, Università degli Studi, Ancona, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Mazzanti
authors.forename: R A
authors.initials: RA
authors.lastname: Rabini
authors.forename: A M
authors.initials: AM
authors.lastname: Cugini
authors.forename: G
authors.initials: G
authors.lastname: Zolese
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D006801:Humans; D008301:Maleimides / Q000737:chemistry; D010920:Placenta / Q000187:drug effects* / Q000201:enzymology; D011247:Pregnancy; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects* / Q000302:isolation & purification; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013696:Temperature
chemical_list: D008301:Maleimides; D013438:Sulfhydryl Compounds; C043592:maleimide; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium