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Radiation-induced leukocyte entrapment in the rat retinal microcirculation
N Hiroshiba1, Y Ogura, K Sasai
1Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Japan.
Purpose:
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.