Na+-Dependent Uptake and Release of Taurine by Neuroblastoma × Glioma Hybrid Cells |
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Authors: | Konrad Kü rzinger,Bernd Hamprecht |
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Affiliation: | Max-Planck-Institut für Biochemie, Martinsried, F.R.G. |
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Abstract: | Abstract In neuroblastoma × glioma hybrid cells, a cell line of neuronal character, a saturable uptake system for taurine is found which displays high affinity and high capacity ( K m= 38 μ m , V = 1.25 nmol mg−1 min−1)- Only the closely related structural analogues hypotaurine and β-alanine are able to inhibit the transport of radioactively labeled taurine. Imipramine or haloperidol at 100 μ m effectively blocks taurine uptake. High-affinity taurine uptake shows an absolute and highly specific requirement for Na+. The hybrid cells internalize taurine very slowly and, with 1 m m extracellular taurine, attain a plateau only after more than 20 h, at which time approximately 34 m m labeled taurine has accumulated in the cytosol. Generally there is hardly any spontaneous release of accumulated taurine. Efflux can, however, be induced by increasing the intracellular Na+ content and is then accelerated by lowering the extracellular Na+ concentration. The hypothesis is forwarded that taurine may exert its function by driving the extrusion of Na+ in emergency situations. |
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Keywords: | Taurine Neuronal cells High-capacity uptake Release Na+ dependence |
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