Taurine receptors in membranes from retinal pigment epithelium cells in culture

Abstract

[ 3H]Taurine-specific binding to membranes from retinal pigment epithelium was demonstrated. A single saturable system was found, with K B = 237 nM and B max = 2.8 pmol/mg protein. Binding to freshly prepared membranes showed partial Na +-dependence while in frozen/thawed membranes, binding remained unchanged in the absence or presence of this ion. A 30–40% increase in binding was observed at physiological temperature (37°C) compared to 4°C in fresh but not in frozen membranes. Accumulation of taurine was followed during differentiation in vitro; results showed that changes in uptake and receptor binding to frozen membranes are not parallel, discarding the possibility of an interaction with uptake sites. Pharmacology of these binding sites suggests that they could be common to other amino acids, since displacement experiments showed that glycine, β-alanine and strychnine were as potent as taurine itself in displacing [ 3H]taurine. Our data open the possibility of taurine being involved in the communication between the retina and the retinal pigment epithelium through an interaction with specific receptors.