Because of its high concentration in the retina, the characterization as to
where taurine and its transporter are located gives us clues as to its possible
functions in the various cell types of the retina. In several vertebrate species
taurine has been localized to the photoreceptors and pigment epithelium
(Lake et al. 1978). Plasma taurine levels range from 44-62 µM in humans
(Hussain and Voaden 1987a; Trautwein and Hayes 1990; Inoue at al. 2003) to
18 – 89 µM in bovine (Sakai and Nagasawa 1992; Kelly et al. 2000) to 170
nmol/ml in rabbits (El-Sayed et al. 1998). In retinal tissues, taurine is a
dominant amino acid, with concentrations of 410 mmol/kg protein in control
mice, with a precipitous drop to 145 mmol/kg in mice that have diminished
number of photoreceptors (Cohen et al. 1973). In tissues, taurine concentrations
can range from 10 mM in the frog to over 50 mM in rat and rabbit