Retinal degeneration, taurine

Other retin d degenerations that may be confused with toxic reactions in the retina of laboratory species include nutritional retinal degeneration due to taurine deficiency in cats and vitamin E deficiency in dogs. 

Hayes, K.C., Carey, R.E., and Schmidt, S.Y., 1975, Retinal degeneration associated with taurine deficiency in the cat. Science, 188 949-951. 

S. Schmidt, Taurine in retinal degeneration, in "Low molecular weight sulfur-containing natural products. Plenum Press, New York (1979). 

Cats and kittens fed a synthetic diet containing partially-purified casein as the source of protein become taurine deficient and develop retinal degeneration. This degeneration, which eventually results in blindness, can be prevented or reversed by supplementing these diets with taurine but not by supplementation via ostensible taurine precursors, methionine, cysteine or inorganic sulfate (Hayes et al., 1975a,b Schmidt et al., 1976). 

Those human infants fed the currently available synthetic formulas often have taurine-containing foods added to the diet within a few weeks or months of birth, and the time scale for induction of retinal degeneration in the cat is of the order of months. Furthermore, the concentration of taurine in retina of most species, although high, is not as great as in the retina of the cat. This high concentration of taurine may render the cat retina especially vulnerable. 

Retinal degeneration in cats fed casein, II,Supplementation with methionine, cysteine or taurine. Invest.Ophthalmol.. 

Figure 5. Retinal taurine concentrations, ERG amplitudes and retinal DNA concentrations at various postnatal ages in normal Long-Evans rats and pigmented RCS rats with hereditary retinal degeneration.

Berson, E. L., Hayes, K. C., Rabin, A. R., Schmidt, S. Y., and Watson, G. Retinal degeneration in cats fed casein II. Supplementation with methionine, cysteine or taurine. Invest. Ophthalmol. 3 52-58, 1976. 

Schmidt, S. Y., and Berson, E. L. Taurine uptake in isolated retinas of normal rats and rats with hereditary retinal degeneration. 

In contrast to the taurine-deficient cat in which retinal deficiency precedes photoreceptor cell death, decreases in retinal taurine concentrations in the RCS/p+ rat occur simultaneously with photoreceptor cell death after the third week of postnatal life. During early postnatal life, the RCS rat retina develops comparably to that of normal rats, and until about 21-23 postnatal days, the RCS rat retina is similar to normal with respect to the thickness of the outer nuclear layer, retinal DM and taurine concentrations, and ERG amplitudes. After the 23rd postnatal day, the photoreceptor cells begin to degenerate, and thereafter the reductions in retinal taurine content (Figure 5) can be correlated with reduction in the thickness of the outer nuclear layer, decrease in retinal DM concentrations, and a decline in ERG amplitudes. 

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