Taurine trophic modulation of goldfish retinal outgrowth and its interaction with the optic tectum |
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Authors: | S Cubillos L Lima |
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Institution: | (1) Laboratorio de Neuroquímica, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas, Venezuela |
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Abstract: | Summary. Goldfish retinal explant outgrowth in the presence of fetal calf serum is stimulated by taurine. In the absence of it, but
with glucose in the medium, length of neurites is still elevated by the amino acid. Using the medium in the presence of glucose,
but in the absence of fetal calf serum, we explored the effect of optic tectum medium from cultures of them coming from goldfish
without crush of the optic nerve or 3, 5, 10, 14 and 20 days after crush. Retinal explants, intact or from goldfish with crush
of the optic nerve 10 days prior to starting the culture, were employed in order to measure the possible effect of optic tectum
media and the inter action with taurine. In other type of experiments the optic nerve was crushed 1, 2, 4, 7 and 10 days before
dissection of the optic tectum, and then co-cultured with intact or 10 days post-crush retinal explants. Optic tectum media
produced a time-dependent effect on outgrowth in lesioned retinas with a maximum effect around 5 days after the lesion for
the corresponding optic tectum. Taurine, 4 mM, did not further affect the outgrowth in the presence of optic tectum media,
but did significantly increase length of neurites either in intact or in post-lesion retinas. Co-culture of optic tectum at
different days post-lesion and retinas at 10 days post-lesion increased the outgrowth around 4 days post-lesion, in a preparation
resulting in mutual effects of both types of tissues. The addition of taurine in these conditions did not further increase
outgrowth, rather inhibited it according to the time after lesion of optic nerve corresponding to the co-cultured optic tectum.
The effect of taurine was concentration-dependent, since 0.2 mM was more effective than 2 or 4 mM in the presence of optic
tectum with lesion of 2 days. These results demonstrate the time-course of the regeneration processes in the visual system
of goldfish, indicating the crucial periods after crush in which the tectum could produce stimulation and later decrease or
no effect on outgrowth from the retina. In addition, they are evidences of the interaction between taurine and optic tectum
production of time-produced specific agents. The mechanisms underlying these effects are closely related to calcium, as it
was demonstrated by the addition of extracellular or intracellular chelators to the medium, which inhibited the effects of
the optic tectum and the trophic properties of taurine in this system. The inhibitor of taurine transport, guanidoethylsulfonate,
also decreased the stimulatory effects of the optic tectum and of taurine, indicating an interaction of substances produced
by the tectum with taurine, and an effect of taurine mediated through its entrance to the cells. Overall, retinal explants
outgrowth in the absence of fetal calf serum, the interaction of agents of the optic tectum and taurine modulates outgrowth
from the retina, and these effects are mediated by calcium levels and by the levels of intracellular taurine. |
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Keywords: | : Co-culture – Optic nerve crush – Optic tectum – Retinal outgrowth – Taurine |
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