Modification of the Rate of Ouabain Binding to (Na++ K+)ATPase by Lithium Ions |
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Authors: | Nagaswamy Krishnan R Wayne Albers |
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Institution: | Department of Neuroscience and Center for Neurobiological Sciences, University of Florida College of Medicine, Box J-244, J. H.M. Health Center, Gainesville, Florida 32610, U.S.A.;Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190, U.S.A. |
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Abstract: | We report on the interactions of Li+, a congener of K+ with the (Na+ + K+)-ATPase from E Electricus as measured by their effects on the rate of 3H]-ouabain binding to this enzyme. Like K+, Li+ slows ouabain binding under both Type I (Na+ + ATP) and Type II (P1) conditions, but with lower affinity. In contrast to K+, the Li+ inhibition curve is hyperbolic, suggesting interaction at an uncoupled site. Also differing from the complete inhibition by high K+, a residual ouabain-binding rate persists at high Li+. The interactions of Li+ and K+ are synergistic: the apparent K+ affinity increases 3 to 4-fold in presence of Li+. These results are consistent with the conclusion that Li+ interacts with only one of the two K+ sites and may be of interest in interpreting lithium pharmacology. |
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Keywords: | Estrogen Polyamines Hypothalamus Pituitary |
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