Effects of zinc ex vivo and intracellular zinc chelator in vivo on taurine uptake in goldfish retina.

Taurine and zinc exert neurotrophic effects. Zinc modulates Na(+)/Cl(-)-dependent transporters. This study examined the effect of zinc (ZnSO(4)) ex vivo and zinc chelator N,N,N',N'-tetrakis-(2-pyridylmethyl) ethylenediamine (TPEN) in vivo on [(3)H]taurine transport in goldfish retina. The effect of TPEN in vivo on taurine and zinc levels was determined. Isolated cells were incubated in Ringer with zinc (0.1-100 microM). Taurine transport was done with taurine (0.001-1 mM) and 50 nM [(3)H]taurine. Zinc (100 microM) noncompetitively inhibited taurine transport. TPEN was administered intraocularly and retinas extracted 3, 5 and 10 days later. Taurine was determined by HPLC (nmol/mg protein) and zinc by spectrophotometry ICP (mg/mg protein). Taurine and zinc levels decreased at 3 days and increased at 10 days after TPEN administration. At 10 days after intraocular TPEN, taurine transport affinity increased (K (s) = 0.018 +/- 0.006 vs. 0.028 +/- 0.008 mM). Apparently, zinc deficiency affects the taurine-zinc complex and taurine availability. The increased taurine uptake affinity by TPEN was possibly associated with a response to maximize retinal taurine content at low zinc concentration.