title: Effect of Li+ and Ba2+ on the electrocyte membrane-bound (Na+ + K+)-ATPase.
abstract: Membrane-bound (Na+ + K+)-ATPase activity from the non-innervated and innervated faces of Electrophorus electricus (L.) electric organ, obtained by differential centrifugation, was measured using AChE as an enzyme marker for membranes derived from the post-synaptic area (fraction P3) of the electrocyte. The effect of Li+ and Ba2+ on (Na+ + K+)-ATPase activity of the two membrane fractions (P2 and P3) was analysed with respect to K+ and Mg2+ ions, after the I50 estimation. The kinetics of the reactions with these cations were investigated showing that Li+ inhibits P2 uncompetitively and for P3 presented a mixed type inhibition. Ba2+ behaved as an hyperbolic mixed type inhibitor for P2 and a linear mixed type inhibitor for P3 fraction.
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology*; D002412:Cations; D002462:Cell Membrane / Q000201:enzymology; D004557:Electric Organ / Q000201:enzymology*; D004593:Electrophorus / Q000378:metabolism*; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
chemical_list: D002412:Cations; D001464:Barium; D008094:Lithium; D000254:Sodium-Potassium-Exchanging ATPase