Radiation-induced leukocyte entrapment in the rat retinal microcirculation.
OBJECTIVE
To evaluate the effects of irradiation on leukocyte dynamics in the rat retinal microcirculation.


METHODS
Thirty-five Brown-Norway rats received a dose of 10 Gy irradiation in one fraction. Leukocyte dynamics were studied with acridine orange digital fluorography, in which a nuclear fluorescent dye of acridine orange is used and examined by scanning laser ophthalmoscope. This technique allowed visualization of fluorescent leukocytes in vivo. The leukocyte dynamics were evaluated at 0, 4, 7, 14, 30, and 60 days after the irradiation.


RESULTS
Mean leukocyte velocity in the retinal capillaries decreased immediately. It partially recovered on day 4 but then gradually decreased up to the 2-month mark. Low-dose irradiation induced entrapment of leukocytes in the retinal microcirculation. The number of entrapped leukocytes gradually increased with time. The major retinal vessels significantly constricted immediately after irradiation. The diameter was reduced by 76% in arteries and 75% in veins, 2 months after irradiation.


CONCLUSIONS
Entrapped leukocytes may be activated and exacerbate vascular injury and microinfarction and thus may participate in the pathogenesis of radiation retinopathy.
Hiroshiba
N
N
Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Japan.
Ogura
Y
Y
Sasai
K
K
Nishiwaki
H
H
Miyamoto
K
K
Hamada
M
M
Tsujikawa
A
A
Honda
Y
Y
D000165:Acridine Orange; D000818:Animals; D002196:Capillaries / Q000528:radiation effects; D001330:Electronic Data Processing; D005456:Fluorescent Dyes; D007091:Image Processing, Computer-Assisted; D007834:Lasers; D007962:Leukocytes / Q000502:physiology* / Q000528:radiation effects*; D008297:Male; D009887:Ophthalmoscopy; D051381:Rats; D011914:Rats, Inbred BN; D012171:Retinal Vessels / Q000502:physiology / Q000528:radiation effects*; D013997:Time Factors; D014661:Vasoconstriction / Q000502:physiology
D005456:Fluorescent Dyes; D000165:Acridine Orange