The effect of iodide iontophoresis on the antioxidative capacity of the tear fluid.

BACKGROUND: Environmental oxidative stress changing the properties of the tear fluid can lead to keratoconjunctivitis sicca (dry eye syndrome). The aim of this study was to determine whether iodide iontophoresis influences the antioxidative capacity (ACW = water soluble antioxidative capacity) of the tear fluid, and to compare iodide iontophoresis with other balneotherapeutic measures. METHODS: This prospective study evaluated 92 patients in four groups. Twenty-four patients were treated with iodide iontophoresis, 24 with other balneotherapeutic methods. Twenty-five patients received iodide iontophoresis combined with other balneotherapeutic methods and 21 persons received no treatment (control). Unstimulated tear fluid, serum and urine were collected. ACW was determined photochemically in tear fluid and serum; iodine was measured in urine photometrically. RESULTS: Iodide iontophoresis increases the ACW of the tear fluid but not the ACW of the serum. Other iodine therapies increase the ACW in serum but not in tear fluid. Iodine excretion in urine was increased in all treated groups compared to the control. CONCLUSION: The increase of ACW in tear fluid after iodide iontophoresis can support the defense mechanism of the eye against oxidative influence effects, which may alleviate the symptoms of keratoconjunctivitis sicca.

Dual method for the determination of peroxidase activity and total peroxides-iodide leads to a significant increase of peroxidase activity in human sera.

Peroxidases are very important enzymes, e.g., as preventive antioxidants by removing noxious peroxides from the blood. For this reason we evaluated a colorimetric method which detects the activity of endogenous peroxidases by their reaction with hydrogen peroxide, using tetramethylbenzidine as the chromogenic substrate. This assay design can be easily reversed by change of the variable compound to measure also total peroxides in plasma or serum. An increased total antioxidant status was reported previously by the addition of iodide to human serum. In this study iodide activated the endogenous peroxidases significantly in comparison to control sera and isomolar NaCl as well as horseradish peroxidase. Corresponding to the increased peroxidase activity a concomitant decrease of total peroxides occurred in the same samples. This exchangeable assay design is a beneficial opportunity to screen total peroxide levels as well as peroxidase activity in human sera without time-consuming preparations. The method proved to be simple and is favorable due to its specificity, reproducibility, and low costs. Moreover, we were able to find an explanation for the increased total antioxidant status in the presence of iodide, which is presumably an indirect protective effect via an enhanced activity of enzymatic antioxidants, thereby reducing endogenous peroxides.