title: The effect of micromolar Ca2+ on the activities of the different Na+/K(+)-ATPase isozymes in the rat myometrium.
abstract: In the present work we show the existence of two Na+/K(+)-ATPase isozymes in rat myometrial microsomes and suggest that they have different Ca2+ sensitivities. The catalytic subunits (alpha 1, alpha 2) of Na+/K(+)-ATPase were labelled by fluorescein-isothiocyanate and separated by SDS gel electrophoresis. The two isozyme Ca2(+)-sensitivities were studied by comparing the kinetics of Ca2+, strophantidin, ouabain and N-ethylmaleimide inhibitions. Our results indicate that the activity of the high ouabain-sensitive part (alpha 2 type) of Na+/K(+)-ATPase enzyme could only be inhibited by micromolar Ca2+. Furthermore, treatment of the microsomal preparation with 1mM N-ethylmaleimide selectively inactivated the high Ca2+ sensitive isoform of myometrial Na+/K(+)-ATPase.
authors.affiliation: Inst. Biochem. I., Semmelweis Univ. Sch. Med. Budapest, Hungary.
authors.forename: A
authors.initials: A
authors.lastname: Turi
authors.forename: J
authors.initials: J
authors.lastname: Somogyi
authors.forename: N
authors.initials: N
authors.lastname: Mullner
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005260:Female; D016650:Fluorescein-5-isothiocyanate; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007527:Isoenzymes / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D046911:Macromolecular Substances; D008861:Microsomes / Q000201:enzymology*; D009215:Myometrium / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013327:Strophanthidin / Q000494:pharmacology; D013861:Thiocyanates
chemical_list: D005452:Fluoresceins; D005456:Fluorescent Dyes; D007527:Isoenzymes; D046911:Macromolecular Substances; D013861:Thiocyanates; D012967:Sodium Dodecyl Sulfate; D010042:Ouabain; D013327:Strophanthidin; D000254:Sodium-Potassium-Exchanging ATPase; D016650:Fluorescein-5-isothiocyanate; D005033:Ethylmaleimide; D002118:Calcium; D004121:Dimethyl Sulfoxide