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.

Localization of taurine transporter, taurine, and zinc in goldfish retina.

Taurine and zinc interact during structural and functional development of the rat retina and during the process of regeneration of retinal fragments from goldfish. These observations formed the basis for evaluating the regional correlation between the localization of the taurine transporter, taurine content and labile zinc content in goldfish retina. In the retina, the taurine transporter is expressed in photoreceptors, the outer plexiform layer, the inner nuclear layer and the ganglion cell layer. Taurine was detected in photoreceptors, the outer and inner nuclear layers, the outer plexiform layer and the ganglion cell layer. A large amount of labile zinc was detected in photoreceptors and to a lesser extent in ganglion cells. The taurine transporter, taurine and zinc coexist in photoreceptors and the ganglion cell layer. Their co-localization in photoreceptors may be related to the neuro-protective role of taurine and zinc in this layer. By contrast, their co-existence in ganglion cells may be related to their involvement in cell differentiation, development, and regeneration. This reveals the importance of taurine and zinc in maintaining normal cellular function in these particular layers of the retina.

Neuritic outgrowth from goldfish retinal explants, interaction of taurine and zinc.

Various studies provide evidence for an interaction between taurine and zinc during development, affecting the morphology and function of the retina. The objectives of the present work were to determine taurine and zinc levels in the retina of goldfish during regeneration and to investigate the effect of the intracellular zinc chelator N,N,N,N-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) on the trophic role of taurine on outgrowth from post-crush goldfish retinal explants. Taurine was determined by HPLC (nmol/mg protein) and zinc by spectrophotometry ICP (microg/mg protein) at various days post-crushing the optic nerve. The levels of taurine were significantly increased at 72 h and the zinc levels at 24 h. Explants from retinas, 10 days post-crush, were cultured for 5 days in the presence of various concentrations and combinations of TPEN and taurine. TPEN, 1 nM, decreased the outgrowth but simultaneously with taurine (1-8 mM) there was an increase. These results demonstrate that zinc was necessary for normal outgrowth of retinal fibers and that taurine counteracted the chelator effect.

Respuestas inmunológicas y de enzimas antioxidantes en la ostra perla Pinctada imbricata (molusca: pteridae) expuesta a niveles subletales de fuel oil N#6 / Immunologic answers and of anti-rust enzymes in the oyster pearl Pinctada imbricata (molusca pteridae) exposed at levels subletales of fuel oil N#6

Se evaluó las respuestas inmunológicas y de sistemas enzimáticos antioxidantes que participan en el control de toxicidad de oxidoradicales en la ostra perla Pinctada imbricata, después de la exposición aguda (7d) a 25 y 100 por ciento de la fracción soluble de Fuel Oil N#6 (FSA), una fuente de hidrocarburos poliaromáticos y de metales pesados en los ecosistemas marinos. La actividad de lisozimas en glándula digestiva en la fagocitosis en los hemocitos ueron determinadas como respuestas inmunológicas humoral y celular, respectivamente, usando levaduras muertas por calos como antígeno para el ensayo de la fagocitosis. La variabilidad y el número total de hemocitos también fueron determinados. Las enzimas antioxidantes glutationa transferasa (GST), glutationa reductasa (GR), glutationa peroxidasa (GPx) y catalasa (CAT), glutationa reductasa (GR), glutationa de glándula digestiva y manto. En la glándula digestiva, la exposición a FSA incrementó significativamente las actividades de GTS y CAT. En el manto se produjo un aumento en la actividad de GPx y descenso en las actividades de GST y GR, mientras que CAT no fue afectada. A excepción de la viabilidad celular a la exposición del 100 por ciento FSA, los indicadores inmunológicos no fueron afectados por el contaminante. Los resultados muestran la sensibilidad de las enzimas antioxidantes de la glándula digestiva y manto a la exposición subletal aguda de Fuel Oil N#6, sugiriendo un incremento en el flujo de oxiradicales y posibles manifestaciones bioquímicas perjudiciales asociadas con estrés oxidativo en ambos tejidos. Estos parámetros pueden ser utilizados como herramientas potenciales para el estudio de la toxicidad de contaminantes en el medio marino