In vivo toxicity study of rhodamine 6G in the rat retina.
OBJECTIVE
To investigate the intraocular effect of rhodamine 6G (R6G) on retinal structures and function in an in vivo rat model and to develop an in vivo method for accurate evaluation of new dyes for intraocular surgery.


METHODS
R6G in physiologic saline solution (PSS) was injected into the vitreous of adult Brown Norway rats at concentrations of 0.0002%, 0.002%, 0.02%, 0.2%, and 0.5%. Control animals received only PSS. Retinal toxicity was assessed by retinal ganglion cell (RGC) counts, light microscopy 7 days later, photopic electroretinography (ERG), and measurement of scotopic sensitivity and recovery of dark adaptation 48 hours and 7 days after intravitreous injection.


RESULTS
R6G at concentrations of 0.2% and 0.5% led to a dose-dependent loss of RGC. The most significant loss occurred at 0.5%. Lower concentrations (0.0002%, 0.002%, and 0.02%) produced no statistically significant retinal ganglion cell loss. Analysis of the eyes by light microscopy showed no structural changes in the central retina, although injections of 0.5% R6G were followed by impressive degenerative changes adjacent to the injection sites. ERGs showed no effects of the highest R6G concentration on rods, kinetics of rhodopsin recovery after bleaching, or cone-driven responses.


CONCLUSIONS
R6G can be safely injected in doses of up to 0.02% in rats, but has a toxic effect on retinal ganglion cells at higher concentrations. Accumulation of R6G may be a problem at higher concentrations, particularly at the injection site.
Thaler
Sebastian
S
Centre for Ophthalmology, Division of Experimental Ophthalmology, University of Tübingen, Röntgenweg 11, Tübingen, Germany. sebastian.thaler@uni-tuebingen.de
Haritoglou
Christos
C
Choragiewicz
Tomasz J
TJ
Messias
Andre
A
Baryluk
Aneta
A
May
C Albrecht
CA
Rejdak
Robert
R
Fiedorowicz
Michal
M
Zrenner
Eberhart
E
Schuettauf
Frank
F
D000818:Animals; D002452:Cell Count; D003623:Dark Adaptation; D004305:Dose-Response Relationship, Drug; D004596:Electroretinography / Q000187:drug effects*; D005456:Fluorescent Dyes / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D009991:Oscillometry; D051381:Rats; D011914:Rats, Inbred BN; D012160:Retina / Q000187:drug effects* / Q000473:pathology; D012162:Retinal Degeneration / Q000139:chemically induced* / Q000473:pathology; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000473:pathology; D012235:Rhodamines / Q000008:administration & dosage / Q000633:toxicity*
D005456:Fluorescent Dyes; D012235:Rhodamines; C026188:rhodamine 6G