Effects of osmotic and light stimulation on 3H-taurine efflux from isolated rod outer segments and synthesis of tauret in the frog retina

Study of taurine and tauret content in the compound eye of locust with light and dark adaptation

Taurine as well as tauret (retinyliden taurine) levels were measured in locust Locusta migratoria compound eyes. HPLC measurements revealed relatively low taurine levels (1.9 +/- 0.16 mM) in dark-adapted eyes. Glutamate, aspartate and glycine levels were 2.0 +/- 0.2, 2.7 +/- 0.4 and 3.0 +/- 0.37 mM, respectively, while GABA was present only in trace amounts. After about 4 h of light adaptation at 1500-2000 lx, amino acid levels in the compound eye were as follows: taurine, 1.8 +/- 0.17 mM; glutamate, no change at 2.1 +/- 0.2 mM; aspartate sharply increased to 4.7 +/- 0.7 mM; glycine slightly decreased to 2.8 +/- 0.3 mM; and GABA trace levels. In the compound eye of locust Locusta migratoria, the existence of endogenous tauret in micro-molar range was established. In the dark, levels were several times higher compared with compound eye after light adaptation 1500 lx for 3 h, as estimated by TLC in combination with spectral measurements. Existence of tauret in compound eye is of special interest because in the compound eye, rhodopsin regeneration is based on photoregeneration.