Effects of zinc ex vivo on taurine uptake in goldfish retinal cells.
BACKGROUND
Taurine and zinc exert neurotrophic effects in the central nervous system. Current studies demonstrate that Na+/Cl- dependent neurotransmitter transporters, similar to that of taurine, are modulated by micromolar concentrations of zinc. This study examined the effect of zinc sulfate ex vivo on [3H]taurine transport in goldfish retina.


METHODS
Isolated cells were incubated in Ringer with zinc (0.1-100 microM). Taurine transport was done with 50 nM [3H]taurine or by isotopic dilution with taurine (0.001-1 mM) and 50 nM [3H]taurine.


RESULTS
Zinc reduced the capacity of taurine transport without changes in affinity, and caused a noncompetitive inhibition of high affinity taurine transport, with an EC50= 0.072 microM. The mechanism by which zinc affects taurine transport is unknown at the present.


CONCLUSIONS
There may be a binding site of zinc in the transporter that affects union or translocation of taurine, or possibly the formation of taurine-zinc complexes, rather than free zinc, could affect the operation of the transporter.
Nusetti
Sonia
S
Laboratorio de Neuroquímica, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela. snusetti@yahoo.com
Urbina
Mary
M
Lima
Lucimey
L
D000818:Animals; D006054:Goldfish; D008562:Membrane Glycoproteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D011869:Radioligand Assay; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013654:Taurine / Q000378:metabolism*; D019287:Zinc Sulfate / Q000494:pharmacology*; D000099247:Taurine Transporters
D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D013654:Taurine; D019287:Zinc Sulfate; D000099247:Taurine Transporters
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