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Taurine Stimulation of Isolated Hamster Brain Na + , K + ‐ATPase: Activation Kinetics and Chemical Specificity
Author(s) -
Hastings David F.,
Welty Joseph D.,
Rohani Farrokh
Publication year - 1985
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1985.tb07166.x
Subject(s) - taurine , chemistry , choline , cytosol , biochemistry , atpase , stimulation , ouabain , activator (genetics) , amino acid , biology , enzyme , receptor , endocrinology , sodium , organic chemistry
Epileptic foci are associated with locally reduced taurine (2‐aminoethanesulfonic acid) concentration and Na + , K + ‐ATPase (EC 3.6.1.3) specific activity. Topically applied and intraperitoneally administered taurine can prevent the development and/or spread of foci in many animal models. Taurine has been implicated as a possible cytosolic modulator of monovalent ion distribution, cytosolic “free” calcium activity, and neuronal excitability. Taurine may act in part by modulating Na + , K + ‐ATPase activity of neuronal and glial cells. We characterized the requirements for in vitro modulation of Na + , K + ‐ATPase by taurine. Normal whole brain homogenate Na + , K + ‐ATPase activity is 5.1 ± 0.4 (4) μmol P i ± h −1 ± mg −1 Lowry protein. Partial purification of the plasma membrane fraction to remove cytosolic proteins and extrinsic proteins and to uncouple cholinergic receptors yields a membrane‐bound Na + , K + ‐ATPase activity of 204.6 ± 5.8 (4) mol P i ± h −1 ± mg −1 Lowry protein. Taurine activates the Na + , K + ‐ATPase at all levels of purification. The concentration dependence of activation follows normal saturation kinetics ( K 1/2 = 39 mM taurine, activation maximum =+87%). The activation exhibits chemical specificity among the taurine analogues and metabolites: taurine = isethionic acid > hypotaurine > no activation =β‐alanine = methionine = choline = leucine. Taurine can act as an endogenous activator/modulator of Na + , K + ‐ATPase. Its action is mediated by a membrane‐bound protein.