Retina taurine role

The high concentration of taurine in cells is an indication that it is an important molecule but not all functions or their importance are known. Cell membranes are impermeable to taurine so that it must be formed in the cell, within which its concentration is very high. The concentration ratio across the membrane is also very high in cells in the retina (400), neurones in the brain (500) and in some tumour cells (7000). Unfortunately, the precise role of taurine in these particular cells is not known. Of the many functions that are known (Huxtable, 1992 Schuller-Levis Park, 2003) the following is a summary ... 

The role of taurine in the retina has been thoroughly reviewed elsewheref( and is the subject of several papers at this meeting It is of interest that taurine uptake into platelets from patients with retinitis pigmentosa has recently been shown to be decreased-. Platelets are considered to be useful models for synaptosomes in the central nervous system and have been much used in tudies of the uptake mechanisms of various biogenic amines. Since retinitis pigmentosa may also be found in patients with Friedreich s ataxia, it would be of interest to examine the transport and content of taurine in platelets from patients. 

Although various physiological roles were suggested for taurine in different tissues like brain, heart, retina, the origin of this substance in these tissues is still unclear. Taurine could be provided by the diet and could also be synthesized. Until now, three main pathways were described or postulated in mammals for this biosynthesis ... 

Pasantes-Morales, H., Klethi, J., Urban, P. F., and Mandel, P., 1972, The physiological role of taurine in retina Uptake and effect on electroretinogram (ERG), Physiol. Chem. Phys. U 339. 

Although the precise role of taurine In retina Is not completely known there Is evidence that It can play an Inhibitory transmitter pole (16, 17) since It Is able to affect potassium and calcium fluxes at the Ionic membrane level (18-20), At the light of these findings It Is easily Interpreted the functional Inhibitory role of taurine In experiments In which from perfused chick and rat retina preloaded with 35S-taurlne light flashes enhance endogenous and labeled taurine release (21,22), Taurine Is the most potent amino acid able to reversibly abolish electroretinogram b wave (23-25) as well as to depress several neuronal populations from cerebral cortex, subcortical areas and spinal cord (26-29), In addition a specific uptake system has been described to occur In rat retina (30, 31) as well as In retinal pigment epithelium (32) and In slices and synaptosome preparations from various areas of the brain (33, 34),... 

Our methodology show that at the used sucrose gradients pedicle synaptosomes were shrunken and synaptic vesicles were clumping, thus suggesting that further studies with different gradients might enable to avoid these artifacts and better clarify the biochemical mechanisms and functional role of taurine in retina. 

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