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Effects of Monovalent Ions on the Transport of Noradrenaline Across the Plasma Membrane of Neuronal Cells (PC‐12 Cells)
Author(s) -
Harder R.,
Bönisch H.
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.tb05536.x
Subject(s) - vesicle , chemistry , membrane , biophysics , potassium , electrochemical gradient , membrane potential , diffusion , membrane transport , biochemistry , biology , physics , organic chemistry , thermodynamics
The dependence on Na + , K + , and C1 − of uptake and accumulation of [ 3 H]noradrenaline was studied in plasma membrane vesicles isolated from PC‐12 pheochromocytoma cells. Plasma membrane vesicles accumulated [ 3 H]noradrenaline when an inward‐directed gradient for Na + and an outward‐directed gradient for K + were imposed across the vesicle membrane. Under these conditions, initial rates of uptake of [ 3 H]noradrenaline were saturable ( K m = 0.14 μ M ) and inhibited by a series of substrates and inhibitors of “uptake 1 .’ The IC 50 values were positively correlated with those for inhibition of uptake into intact PC‐12 cells. Uptake and accumulation [ 3 H]noradrenaline in plasma membrane vesicles were absolutely dependent on external Na + and C1 − ; they were dependent on an inwardly directed gradient for Na + but less dependent on an inwardly directed gradient for C1 − . Internal K + strongly enhanced uptake and accumulation of [ 3 H]noradrenaline. Rb + , but not Li + , had the capacity to replace internal K + . Two explanations are proposed for this effect of internal K + : (a) creation of a K + diffusion potential (inside negative) provides a driving force for inward transport, and/or (b) K + increases the turnover rate by formation of a highly mobile potassium–carrier complex. A hypothetical scheme for the transport of noradrenaline is presented.