Taurine in the interphotoreceptor matrix

TAURINE IN THE INTERPHOTORECEPTOR MATRIX Gueli Maria Concetta Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNEC), Università degli Studi di Palermo Taurine (Tau) is the most abundant amino compound free in the retina. It is concentrated in the photoreceptor inner segment, in the outer nuclear layer and in the synapses. The retina synthesizes and receives Tau from choroidal blood via the pigment epithelium (PE). The high content in the retina suggest the possibily of verifying whether it was present in the interphotoreceptor matrix (IPM), which occupies the subretinal space. In this study we have determined the Tau level in the IPM, separating it from other soluble amino compounds. Bovine eyes were obtained from local slaughterhouses and were bisected in darkness. After removal of the vitreos body, the eye cup was washed with 0.14 M NaCl-5mM sodium phosphates, pH 7.4. Preparation of the IPM was carried out by detaching the retina from eye cup using the method of Pfeffer,1983. PE were collected using the method of Feeney-Burns, 1982. Retinas deprived of IPM were homogenized using 0.32 M sucrose-50 mM phosphates, pH 7.2. Free amino compounds in the various preparations were separated using the procedure described by Borum, 1985. Levels of Tau in bovine IPM; PE (homogenate and sonicated); retina (homogenate and sonicated) were (804.10 ± 79.22; 83.91 ± 7.90 and 85.30 ± 8.20; 5,170.50 ± 314.82 and 5,209.00 ± 498.00 nmoles/eye), respectively. The chromatographic profile of a.a. in the IPM was qualitatively more similar to that of retina than to that of PE. As expected, GABA was absent in the PE preparations. It was not surprising to find Tau and amino compounds in the IP space because of the transit role of this retinal area. We believe that three sites could be considered for the origin of Tau in the IPM. One is the PE, which takes up Tau from the blood and accumulates it avidly, to send it via the membrane apical process to photoreceptor cells. The other possible sources are Mùller cells and photoreceptor cells, which have the largest Tau pool. In conclusion, the great similarity between the amino acid profile in the IPM and in the retina suggests that a pool of amino compounds and Tau might be present in the subretinal space. Among the roles suggested for the IPM is that of a route by which nutrients and other small molecules reach the retinal photoreceptor from the apical process of the PE cells. 46° SIBIOC ROMA 13-15 Ottobre 2014