Effects of Taurine in Cellular Responses to Oxidative Stress in Young and Middle-Aged Rat Liver

: Aging is related with an increased cellular level of lipid peroxides and reactive oxygen species (ROS). The useful effects of taurine as an antioxidant in biological systems have been attributed to its capability to stabilize biomembranes, to scavenge ROS, and to decrease the peroxidation of unsaturated membrane lipids. The aim of the present study was to investigate the effects of taurine on malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx), thioredoxin reductase (TR), and endothelial nitric oxide synthase (eNOS) in young and middle‐aged rat liver. There was not a significant difference in liver MDA levels between the control groups of young and middle‐aged rats (P > 0.05). However, liver GSH levels, and GPx and TR activities between the control groups of young and middle‐aged rats were significantly different (P < 0.05). Liver MDA level was significantly lower in the taurine group of middle‐aged rats (P < 0.05). Liver GSH levels, and GPx and TR activities were significantly increased in the taurine group of middle‐aged rats when compared to the control group (P < 0.05). Liver MDA level was significantly lower in the taurine group of young rats than the ones in the control group (P < 0.05). Liver TR activity was significantly increased in the taurine group of young rats when compared to the control group (P < 0.05). Liver GPx activity was not statistically different between the taurine and the control groups in young rats (P > 0.05). Liver GSH levels were not different between the young taurine and the control groups (P > 0.05). Immunohistochemical studies exhibited no change in eNOS activity after taurine injection in young rats. However, in middle‐aged rats, taurine lowered the eNOS reactivity to the same level found in young rats. These results suggested that exogenous taurine might play a role in aging by means of its reducing effects on free radical levels in parallel to an increase in the antioxidant capacity.