High lenticular tolerance to ultraviolet radiation-B by pigmented guinea-pig; application of a safety limit strategy for UVR-induced cataract.
OBJECTIVE
The purpose of this study was to determine a threshold measure, maximum tolerable dose (MTD), for avoidance of UVR-B-induced cataract in the pigmented guinea-pig.


METHODS
Thirty pupil-dilated anesthetized young female guinea-pigs, divided into five equal groups, received between 0 and 84.9 kJ/m(2) unilateral UVR-B. Lens extraction and in vitro lens photography occurred 24 hr after exposure. Measurement of intensity of lens light scattering served as quantifying tool for the degree of cataract. Data analysis included regression, using a second order polynomial model. The applied MTD concept was based on the UVR-B dose-response curve obtained for the pigmented guinea-pig. A smaller number of pigmented guinea-pigs, pigmented rats and albino rats underwent morphometric analysis of the anterior segment geometry.


RESULTS
All eyes exposed to UVR-B developed cataract in the anterior subcapsular region. MTD for avoidance of UVR-B-induced cataract was 69.0 kJ/m(2) in the pigmented guinea-pig. Iris was considerably thicker in the guinea-pig than in the rats. Lens blockage by the dilated iris was lowest in the guinea-pig.


CONCLUSIONS
Maximum tolerable dose for avoidance of UVR-B-induced cataract in the pigmented guinea-pig was 69.0 kJ/m(2), over 10-fold higher than the threshold 5 kJ/m(2) obtained by Pitts et al. in the pigmented rabbit. Maximum tolerable dose is an appropriate method for estimation of toxicity for UVR-B-induced cataract in the guinea-pig. The pigmented guinea-pig is significantly less sensitive to UVR-B exposure than the pigmented rabbit and pigmented rat.
Mody
Vino C
VC
St. Erik's Eye Hospital; Karolinska Institutet, Stockholm, Sweden.
Kakar
Manoj
M
Söderberg
Per G
PG
Löfgren
Stefan
S
D000818:Animals; D002386:Cataract / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D005260:Female; D006168:Guinea Pigs; D007908:Lens, Crystalline / Q000503:physiopathology / Q000528:radiation effects*; D008027:Light; D020714:Maximum Tolerated Dose; D010781:Photography; D010857:Pigment Epithelium of Eye / Q000528:radiation effects*; D011829:Radiation Dosage; D011833:Radiation Injuries, Experimental / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D011836:Radiation Tolerance; D051381:Rats; D017207:Rats, Sprague-Dawley; D012542:Scattering, Radiation; D012880:Skin Pigmentation; D014466:Ultraviolet Rays / Q000009:adverse effects*