Retinal degeneration induced by taurine deficiency in light-deprived cats

The effect of light deprivation on the retinal degeneration induced by taurine deficiency in cats was examined in this study. After 25 weeks of taurine-free diet, taurine levels in plasma, retina, heart, cerebellar and cerebral cortex decrease to 16-25% of normal. The ERG a-wave and b-amplitudes also decreased as a consequence of the taurine-free diet. After 15 weeks of taurine-free diet the b-wave amplitude decreased to 36-41% of normal, and after 25 weeks both the a-wave and the b-wave were undetectable. The structure of the outer segments of photoreceptors, examined by electron microscopy appeared disturbed in the taurine-deficient cats, showing disorientation of the disk membranes, vesiculation and swelling. The time course of taurine deficiency and the retinal degeneration pattern were observed in all cats fed the taurine-free diet, irrespective of the conditions of lighting. These results indicate that the morphological and functional disturbances induced by taurine deficiency in cats are independent of the physiological stimulation of the retina by light.