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Potassium‐Stimulated Release of Radiolabelled Taurine and Glycine from the Isolated Rat Retina
Author(s) -
Smith L. F. P.,
Pycock C. J.
Publication year - 1982
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.1471-4159.1982.tb07942.x
Subject(s) - taurine , potassium , retina , calcium , glycine , endocrinology , medicine , chemistry , stimulus (psychology) , biophysics , biology , biochemistry , amino acid , neuroscience , psychology , organic chemistry , psychotherapist
The release of preloaded [ 3 H]glycine and [ 3 H]taurine in response to a depolarising stimulus (12.5‐50 m M KCl) has been studied in the superfused rat retina. High external potassium concentration immediately increased the spontaneous efflux of [3H]glycine, the effect of 50 m M K + apparently being abolished by omitting calcium from the superfusing medium. In contrast, although high potassium concentrations increased the spontaneous emux of [ 3 H]taurine from the superfused rat retina, this release was not evident until the depolarising stimulus was removed from the superfusing medium. The magnitude of this “late” release of [ 3 H]taurine was dependent on external K + concentrations, and appeared immediately after cessation of the stimulus irrespective of whether it was applied for 4, 8, or 12 min. Potassium (50 m M )‐induced release of taurine appeared partially calcium‐dependent, being significantly reduced (p < 0.01) but not abolished by replacing calcium with 1 mM EDTA in the superfusate. High‐affinity uptake systems for both [ 3 H]glycine and [ 3 H]taurine were demonstrated in the rat retina in vitro ( K m values, 1.67 μ M and 2.97 μ M ; V max values, 19.3 and 23.1 nmol/g wet weight tissue/h, respectively). The results are discussed with respect to the possible neuro‐transmitter roles of both amino acids in the rat retina.