Functional Rescue of photoreceptors from the damaging effects of constant light by survival-promoting factors in the rat.
OBJECTIVE
To investigate whether and how survival-promoting agents rescue photoreceptor cell function and morphology from constant light damage, the authors recorded electroretinographic (ERG) responses and examined light micrographs of retinas in those rats given intravitreal injection of midkine (MK) and basic fibroblast growth factor (bFGF) before constant exposure.


METHODS
Albino Sprague-Dawley rats were injected with MK, bFGF, or phosphate-buffered saline (PBS) 2 days before the onset of 1 week of constant light. ERG responses were recorded using white flash stimuli with the intensity range of 4 log units, followed by histologic examinations of retinas, including quantitative assessment of the outer nuclear layer thickness as an index of photoreceptor cell loss.


RESULTS
ERG responses were barely detectable in uninjected eyes after 1 week of constant light. On the other hand, distinct responses were recordable in eyes injected intravitreally with MK and bFGF, and the degree of ERG rescue in terms of the amplitude of b-wave was approximately 40% to 60% compared with normal eyes. Intravitreally injected PBS showed slight, but noticeable, preservation of ERG responses as well. Histologic examination revealed that MK and bFGF protected photoreceptors from light damage. A good correlation was found between anatomic rescue of photoreceptors as assessed by outer nuclear layer thickness and the functional rescue as defined by the magnitude of ERG responses.


CONCLUSIONS
Functional and anatomic rescue of photoreceptors in albino rats from constant light damage is achieved by prior intravitreal injection of MK and bFGF.
Masuda
K
K
Department of Ophthalmology, Hamamatsu University, School of Medicine, Japan.
Watanabe
I
I
Unoki
K
K
Ohba
N
N
Muramatsu
T
T
D000818:Animals; D002352:Carrier Proteins / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D016207:Cytokines / Q000494:pharmacology; D004596:Electroretinography; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D007267:Injections; D008027:Light / Q000009:adverse effects*; D000078792:Midkine; D010786:Photoreceptor Cells / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D011833:Radiation Injuries, Experimental / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012162:Retinal Degeneration / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*
D002352:Carrier Proteins; D016207:Cytokines; D016222:Fibroblast Growth Factor 2; D000078792:Midkine