Regulation of taurine transporter activity in cultured rat retinal ganglion cells and rat retinal Muller cells

ABSTRACT

Diabetic retinopathy is one of the most common complications of diabetes. The amino acid taurine is believed to play an antioxidant protective role in diabetic retinopathy through the scavenging of the reactive species. It is not well established whether taurine uptake is altered in retinal cells during diabetic conditions. Thus, the present study was designed to investigate the changes in taurine transport in cultures of rat retinal Muller cells and rat retinal ganglion cells under conditions associated with diabetes. Taurine was abundantly up taken by rat retinal Muller cells and rat retinal ganglion cells under normal glycemic condition. Taurine was actively transported to rat Muller cells and rat retinal ganglion cells in a Na + and CI - dependent manner. Taurine uptake further significantly elevated in both types of cells after the incubation with high glucose concentration. This effect could be attributed to the increase in osmolarity. Because nitric oxide [NO] is a molecule implicated in the pathogenesis of diabetes, we also determined the activity of the taurine transporter in cultured rat retinal Muller cells and rat retinal ganglion cells in the presence of the NO donors, SIN-1 and SNAP. Taurine uptake was elevated above control values after 24-h incubation with low concentration of NO donors. We finally investigated the ability of neurotoxic glutamate to change taurine transporter activity in both types of cells. Uptake of taurine was significantly increased in rat retinal ganglion cells when only incubated with high concentration of glutamate. Our data provide evidence that taurine transporter is present in cultured rat retinal ganglion and Muller cells and is regulated by hyperosmolarity. The data are relevant to diseases such as diabetes and neuronal degeneration where retinal cell volume may dramatically change