A morphometric study of light-induced damage in transgenic rat models of retinitis pigmentosa.
OBJECTIVE
To determine relative susceptibility to, and regional variation of, light-induced retinal damage in two rhodopsin-mutant rat models of retinitis pigmentosa, using slow- and fast-degenerating lines.


METHODS
Transgenic S334ter (lines 4 and 9) and P23H (lines 2 and 3) rats were reared in dim cyclic light or darkness and then exposed to intense green light for 1 to 8 hours. Sections along the vertical meridian were collected for retinal morphology and photoreceptor morphometry 2 weeks later. Unexposed transgenic and normal Sprague-Dawley rats served as the control. Mean outer segment lengths and outer nuclear layer thicknesses were analyzed as a function of position along the vertical meridian and as averages across that vector.


RESULTS
Rapidly degenerating S334ter-4 retinas, reared in dim cyclic light, exhibited no light-induced damage, whereas retinas in the other sublines sustained damage within a sensitive region in the superior hemisphere. Light-induced damage always involved loss of outer segment membrane and photoreceptors. In some cases, the retinal pigment epithelium and inner nuclear layer were also affected. Potentiation of light-induced damage by dark-rearing was increased by at least a factor of three, and in some sublines the sensitive region was enlarged to include the entire vertical meridian.


CONCLUSIONS
A complex pattern of light-induced damage outcomes was identified in S334ter (sublines 4 and 9) and P23H (sublines 2 and 3) rats. The relative susceptibilities of each subline to damage by light were different, even within the same transgene, but consistent factors included a sensitive region in the superior hemisphere and potentiation by dark-rearing.
Vaughan
Dana K
DK
University of Wisconsin Oshkosh, Department of Biology, Oshkosh, Wisconsin 54901, USA. vaughan@uwosh.edu
Coulibaly
Sylvie F
SF
Darrow
Ruth M
RM
Organisciak
Daniel T
DT
D000818:Animals; D030801:Animals, Genetically Modified; D008027:Light; D010857:Pigment Epithelium of Eye / Q000473:pathology / Q000528:radiation effects; D011833:Radiation Injuries, Experimental / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D012165:Retinal Ganglion Cells / Q000473:pathology / Q000528:radiation effects; D012174:Retinitis Pigmentosa / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000473:pathology / Q000528:radiation effects
D012243:Rhodopsin