The entry of taurine into the neural retina and pigment epithelium of the frog.

Autoradiographs of frog retinas incubated with radioactively labelled taurine show heavy grain density over (i) cells in the position of amacrine interneurones, (ii) the inner plexiform (synaptic) regions, giving a striated appearance, (iii) photoreceptor cells and their synaptic terminals, and (iv) the pigment epithelium. The inner retina, the photoreceptor cell layer and the pigment epithelium all have uptake systems for taurine with apparent Km's in the high affinity range (Km, 20-50 micron; Vmax, 13-33 nmoles/g/min). In vivo subcutaneously injected taurine was taken up by the pigment epithelium and then passed to the photoreceptors and inner retina over about 10 days. The total level of nucleide in the retina remained constant for at least 6 weeks. There was little or no metabolism of the labelled taurine during this time.