Mass alteration in the lens after exposure to radiation in the 300 nm wavelength region

Ultraviolet radiation-induced cataract in mice: the effect of age and the potential biochemical mechanism

PURPOSE

To study the effect of age on the morphologic and biochemical alterations induced by in vivo exposure of ultraviolet radiation (UV).

METHODS

Young and old C57BL/6 mice were exposed to broadband UVB+UVA and euthanized after 2 days. Another batch of UV-exposed young mice was monitored for changes after 1, 2, 4, and 8 days. Age-matched nonexposed mice served as controls. Lens changes were documented in vivo by slit-lamp biomicroscopy and dark field microscopy photographs ex vivo. Lens homogenates were analyzed for glutathione (GSH) level, and the activities of thioredoxin (Trx), thioltransferase (TTase), and glyceraldehyde-3-phosphate dehydrogenase (G3PD). Glutathionylated lens proteins (PSSGs) were detected by immunoblotting using GSH antibody. Western blot analysis was also done for the expression levels of TTase and Trx.

RESULTS

Both age groups developed epithelial and superficial anterior subcapsular cataract at 2 days postexposure. The lens GSH level and G3PD activity were decreased, and PSSGs were elevated in both age groups, but more prominent in the older mice. TTase and Trx activity and protein expression were elevated only in the young mice. Interestingly, lens TTase and Trx in the young mice showed a transient increase, peaking at 2 days after UV exposure and returning to baseline at day 8, corroborated by lens transparency.

CONCLUSIONS

The lenses of old mice were more susceptible to UV radiation-induced cataract. The upregulated TTase and Trx likely provided oxidation damage repair in the young mice.

Evolution of light scattering and redox balance in the rat lens after in vivo exposure to close-to-threshold dose ultraviolet radiation

PURPOSE

To investigate the evolution of cataract development and glutathione redox balance in the rat lens after in vivo close-to-threshold dose exposure to ultraviolet radiation (UVR) around 300 nm.

METHODS

Three groups of 10 Sprague-Dawley rats were unilaterally exposed to 8 kJ/m² UVR-300 nm for 15 min, and a fourth group of 10 rats was kept without UVR exposure as nonexposed control animals. The exposed animals were killed at 1, 3 and 7 days after exposure. Both lenses from all animals were extracted and photographed and the intensity of forward light scattering was measured quantitatively. Thereafter, the lenses were homogenized. The concentration of reduced glutathione (GSH) and oxidized glutathione (GSSG), and the activity of glutathione reductase (GR) and glutathione peroxidase (GPx), respectively, were determined spectrophotometrically. The mean paired differences between exposed and nonexposed lenses were used as primary data in the statistical analyses.

RESULTS

All exposed lenses developed cataract. Lens light scattering increased throughout the 7 days after UVR exposure. GSH concentration and GPx rate transiently increased at 1 day after exposure and then decreased throughout follow-up, with GSH concentration having a negative balance at the end. GSSG concentration and GR activity did not change after UVR exposure.

CONCLUSION

In vivo close-to-threshold UVR exposure induces a gradual increase in rat lens opacification/cataract development and time dependently alters the redox balance in the lens.

Surface solar ultraviolet radiation: A theoretical approach of the SUVR reaching the ground in Athens, Greece

Daily total ozone observations made during 1985-1993 by both the Total Ozone Mapping Spectrometer (TOMS) flown on the Satellite Nimbus-7 and the Dobson Spectrophotometer have been used in order to investigate the fluctuations of the daily broad-band and spectral solar ultraviolet radiation reaching the ground. This investigation has been performed by employing a recently developed parametric algorithm for the estimation of the spectral and broad-band solar ultraviolet radiation which takes the total ozone variations into consideration. Total ozone reductions during the summertime from 1985 to 1993 over Athens, Greece (37.6 degrees N, 23.4 degrees E), cause an increase in the ultraviolet irradiance which reaches the ground of 0.54 %, 0.98 %, 2.60 % and 0.79 % per decade for the months of July at 300 nm, 312 nm, 320 nm and UVB (280-320 nm), respectively.

Sodium and potassium in the lens after exposure to radiation in the 300 nm wavelength region

The possible change in sodium and potassium concentration in the lens after an in vivo exposure to radiation in the 300 nm wavelength region was investigated. Both lenses from 12 reference rats and from 80 unilaterally exposed rats were examined. The exposed rats were sacrificed in four groups: 6, 24, 72 and 168 h after exposure. The lenticular cation contents were determined using atomic absorption spectrophotometry. In exposed lenses the concentration of sodium increases whereas that of potassium decreases as the time after exposure increases. The rates of concentration change decrease as the time after exposure increases. The increase in sodium precedes the decrease in potassium. Furthermore, a slight increase in the concentration of sodium is registered, as the time after exposure increases, in the non-exposed contralateral lenses. The registered changes are believed to reflect the water balance in the lenses.