Involvement of illumination in indocyanine green toxicity after its washout in the ex vivo rat retina.
OBJECTIVE
To elucidate the involvement of illumination in indocyanine green (ICG) retinal toxicity.


METHODS
We incubated isolated rat retinas with or without illumination after exposure to 0.5% ICG. We also examined whether a time lag following ICG exposure before illumination altered the damage. Toxicity was evaluated by histologic and biochemical assays, including measurement of lactate dehydrogenase release.


RESULTS
Retinas fixed immediately after ICG exposure showed minimal morphologic changes. However, illumination for 3 hours at 34 degrees C starting after washout of ICG selectively damaged the outer nuclear layer. Retinas incubated for 3 hours under the same condition in the dark showed preserved morphology but were damaged by subsequent illumination. When retinas were illuminated after washout of ICG at a lower temperature (30 degrees C), the damage was attenuated. Results obtained using lactate dehydrogenase release were consistent with these morphologic changes.


CONCLUSIONS
Incubating retinas in the dark and cooling after ICG exposure significantly inhibited retinal damage, suggesting that ICG interacts with illumination to induce retinal damage.
Tokuda
Kazuhiro
K
Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Zorumski
Charles F
CF
Izumi
Yukitoshi
Y
D000818:Animals; D004396:Coloring Agents / Q000493:pharmacokinetics / Q000633:toxicity*; D004195:Disease Models, Animal; D005451:Fluorescein Angiography / Q000009:adverse effects; D005453:Fluorescence; D007208:Indocyanine Green / Q000493:pharmacokinetics / Q000633:toxicity*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D012164:Retinal Diseases / Q000209:etiology* / Q000378:metabolism / Q000473:pathology
D004396:Coloring Agents; D007208:Indocyanine Green