Abstract
Purpose: :
RdCVF is a thioredoxin-like protein, derived from rods, that has the potential to rescue cone cells. Light and electron microscopy investigations shows that RdCVF is localized in rod outer and inner segments (ROS and RIS) and outer nuclear layer (ONL). Electron immunohistochemistry was used to specify the fine distribution of RdCVF in the wild albino rat retina after dark and light adaptation, and after light induced retinal damage.
Methods: :
Light adaptation was carried at 400 lux for 3 hours., light damage at 2500 lux white light for 48 hours. Retina samples were fixed with 1.25 % glutaraldeyde then embedded in epon. Ultra thin sections were stained by RdCVF rabbit polyclonal antibodies, conjugated to colloidal gold. Conjugate was prepared by BIOVAR (0014, Yerevan P.Sevag Str. 5/1, Armenia). Ultra thin sections were stained by uranyl acetate. Observations were made using transmission electron microscopy (Philips CM-10 TEM).
Results: :
We produced colloidal gold particles of 20 to 30 nm of diameter. No reaction product could be observed when ultra thin sections were stained with albumin conjugated with colloidal gold. In dark-adapted rat retina, rare immunogold reaction product was noted in the ROS, little more in RIS, more in ONL and few in inner nuclear layer (INL). Light adaptation had no effect on RdCVF distribution. In both conditions, sparsely distributed ROS, RIS, or photoreceptor nuclei show specific reaction product. Light induced damage induces a large increase in the expression of RdCVF. The most dramatic changes were noted 8 days after light damage, when a sharp increase of the RdCVF immunogold reaction product in the rod ONL was observed. Around the nuclei of rod cells a ten-fold increase of immunogold reaction product was measured as compared to dark or light adapted retinas. No noticeable changes were observed in other regions of the layers
Conclusions: :
On the base of RdCVF immunogold electron histochemistry, the fine distribution of RdCVF in the dark and light adapted rat retina was established. RdCVF was localized in the ONL region, to a lesser extend in RIS, ROS and INL. Light adaptation has no effect on the distribution of RdCVF. The sharp increase after light induced damage in the ONL region indicates the possible induction of RdCVF by oxidative stress. This may involve the role of thioredoxin, and RdCVF in the protection against damage generated by intense light.
Keywords: photoreceptors • protective mechanisms • oxidation/oxidative or free radical damage