title: Na+/K+-ATPase from Xenopus laevis (Daudin) kidney and epidermis: high sensitivity towards regulatory compounds.
abstract: Na+/K+-ATPase was prepared from Xenopus laevis epidermis. Purification was obtained by ultracentrifugation on sucrose discontinuous gradient. The maximum of enzyme-containing membranes was concentrated in the denser sucrose layer, exhibiting a good and long-lasting activity (specific activity about 55 mumoles of ATP hydrolyzed/mg of protein/hour). The Kd for the ouabain of kidney and epidermis enzymes were very low (in purified preparations respectively 16 nM for kidney enzyme and 4 nM for skin enzyme), indicating a very high sensitivity toward the cardioglycoside. The dose-response graphs of kidney and skin Na+/K+-ATPase vs ouabain concentrations show that at ouabain concentrations ranging from 1 nM and 1 pM the inhibition elicited by the cardioglycoside disappears and is replaced by an activatory effect. At cardioglycoside concentrations higher than 1 nM, the graphs show the typical inhibition curve.
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004817:Epidermis / Q000201:enzymology; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology; D010042:Ouabain / Q000494:pharmacology; D012867:Skin / Q000201:enzymology*; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014882:Water-Electrolyte Balance; D014982:Xenopus laevis
chemical_list: D012967:Sodium Dodecyl Sulfate; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase