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.