doiSerbia

Reduced glutathione level and gsh-dependent enzyme activities in corticonuclear blocks of lenses in patients with senile cataract

Kisić Bojana (Medicinski fakultet, Institut za biohemiju, Kosovska Mitrovica)
Mirić Dijana (Medicinski fakultet, Institut za biohemiju, Kosovska Mitrovica)
Žorić Lepša (Medicinski fakultet, Klinika za očne bolesti, Kosovska Mitrovica)
Ilić Aleksandra (Medicinski fakultet, Katedra za preventivnu medicinu, Kosovska Mitrovica)
Dragojević Ilija (Medicinski fakultet, Institut za biohemiju, Kosovska Mitrovica)

Introduction. Reduced compound glutathione (GSH) in the lens has the function to protect the thiol group of lens proteins, and as a substrate of glutathione peroxidase (GPx) and glutathione S-transferase (GST). Protein containing thiol groups is significant for the normal function of lens epithelium, i.e. enzymes Na-K-ATP-ase, thus influencing cell permeability. The relationship GSH/GSSG (oxidized glutathione) is normally high in the lens and other ocular tissue owing to the glutathioneredox cycle, which is localized in the lens epithelium and cortex surface. Objective. The aim of the study was to investigate non-enzymic factors of the antioxidant protection of non-protein and protein tiol, as well as to determine glutathione-dependent enzyme activity in the corticonuclear blocks of lenses in patients with senile cataract. Methods. Biochemical studies of lens were carried on 101 patients with senile cataract. According to cataract maturity degree, the patients were classified into two groups: senile incipient cataract (N=41) and mature senile cataract (N=60). GSH concentration was determined by Ellman’s reagent. GPx activity was assayed with cumene hydroperoxide, and that of glutathione S-transferase by follow-up of glutathione conjugation and 1-chloro-2.4-dinitrobenzene rates. Results. A significantly higher GSH concentration was found in the corticonuclear blocks of lenses with initial as related to mature cataract (p<0.001). The activity of enzyme GPx and GST was considerably higher in the corticonuclear blocks of lenses with initial cataract (p<0.001). With cataract progression, the quantity of available GSH, necessary for GPx and GST functioning, declined, so that the activity of these enzymes was also significantly decreased in mature cataract. Conclusion. The determined lower GSH concentration and antioxidant enzyme activity in corticonuclear blocks of lenses, particularly in cataract with a nuclear component, indicate the weakened antioxidant response of lens tissue during the development of senile cataract.

Keywords: cataract, oxidative stress, glutathione, antioxidants