A. BABEȘ, FLORENTINA PLUTEANU

Dept. of Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, Splaiul lndependenţei 91–95, 76201 Bucharest, Romania

Abstract. This paper describes some effects of lyotropic anions on currents generated by the Na recorded in excised inside-out patches from guinea pig cardiac myocytes. We show that these effects are reversible, that ionic strength is a major factor in influencing the pumping tumover and that various anions have effects on the pump current in the presence and in the absence of potassium at the extracellular side. We also report that anions affect the ATP affinity at the catalytic high affinity site, but do not change the dissociation constant for ATP at the low affinity binding site. It is proposed that these effects are related to a change in the local electric field due to anion binding to the lipid membrane or to the protein itself.

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