Objective: To investigate the effects of various concentrations of taurine on streptozotocin (STZ)-induced diabetic cataracts in rats by biochemistry, radioimmunology and capillary zone electrophoresis (CZE).
Methods: One hundred Sprague-Dowley (SD) male rats, weight 180 approximately 200 g, were randomly divided into 5 groups: normal control, STZ plus saline, STZ plus 2% taurine, STZ plus 4% taurine and STZ plus 8% taurine groups. After being fasted for 12 hours, the rats of the STZ group (with or without taurine) were prepared by STZ intraperitoneal injection (55 mg/kg b.w.). Taurine-treated groups received 2%, 4% and 8% taurine injections once daily for 12 weeks (5 ml/kg b.w.). STZ group without taurine received a saline injection once daily for 12 weeks (5 ml/kg b.w.). During the experiment period, blood sugar was measured by ONE TOUCH II. At the end of experiment, several biochemical parameters were measured by Beckman CX-7, insulin was measured by (125)I-insulin radioimmunological detecting kit and the level of taurine in the aqueous humor and the lens was measured by Beckman 5500 capillary zone electrophoresis (CZE) model.
Results: Three weeks after the administration of STZ, the lenses showed vesicle and light opacity in the STZ group. Taurine suppressed the occurrence of early stage cataract obviously. Four to 12 weeks after the administration of STZ, the lens opacity in the 4% and 8% taurine treatment groups was markedly delayed as compared with that of the STZ group. The level of blood glucose in the 4% and 8% taurine groups was decreased evidently compared to that of the STZ group on 4 days, 4 weeks, and 8 weeks (the 4% taurine group). No difference could be detected between the STZ group and taurine treatment groups in 12 weeks. In the 4% and 8% taurine groups, the level of triglycerides decreased markedly compared to that of the STZ group and was near that of the control group. There were no differences of other biochemical parameters among all groups. In the 8% taurine group, the level of taurine in the aqueous humor and lens was increased obviously compared to that of the STZ group (P = 0.036 or P = 0.000, respectively).
Conclusion: The intervening effect of taurine on STZ-induced diabetic cataract is dose-dependent. This effect is not only related to decreases in the levels of blood sugar and triglycerides, but is also related to an increase in the taurine level in the aqueous humor and lens of diabetic rats, which enables the lens to escape from oxidant injury.