Taurine is present in high concentration in the retina of many species including humans. Although its function in retina has not been clarified, a definite connection has been demonstrated between the availability of taurine to the retina and the integrity and function of this tissue. In several species, depletion of taurine leads to abnormal electroretinograms and/or to degeneration of photoreceptor cells. Some of the changes that occur in the retina of taurine-deficient animals resemble those found in the retina of individuals having either inherited retinal degeenrations or receiving retinopathic drugs. These observations suggest that these heterogenous groups of human eye conditions might be related to a defect in taurine availability or utilization. The objectives of this proposal are two fold: (1) to determine whether a defect in taurine availability could be a factor in the onset and progression of inherited retinal degneration and 2) to examine a biochemical involvement of taurine in preserving retinal function. Since acquisition of adequate amounts of retinal tissues is not possible, these studies will employ cultured cell lines derived from individuals with retinitis pigmentosa and from individuals with neurogenetic diseases manifesting retinal degeneration. Cells lines will also be established from relatives without inherited retinal degeneration. The Specific Aims are l) to determine the availabiltiy of taurine, by examining: a) the intracellular concentrations of taurine, b) the de novo synthesis of taurine and c) the kinetics of taurine uptake and taurine efflux. 2) To examine the effect of pharmacological agents known to induce retinal degeneration on taurine uptake and efflux. 3) To determine whether taurine scavenges hypochlorous acid formed by retinal peroxidase. The proposed research should provide insight into the relationship between taurine and the normal function of the retina. The methods used could lead to a relatively non-invasive procedure for preclinical detection of inherited retinal degeneration.