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D.K. Bursell, A.C. Clermont, G. Terrero, B. Gao, S. Rook, L.P. Aiello, E.P. Feener, S.–E. Bursell; Extracellular Carbonic Anhydrase I (CA–I) Induces Retinal Leukocyte Adhesion and Alters Electrophysiology in Non–Diabetic Rat . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3764.
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© ARVO (1962-2015); The Authors (2016-present)
Carbonic anhydrase (Ca) enzymes are known to regulate cellular acid base homeostasis, membrane ion transport, and fluid movement. Intravitreal injection of Ca–I in vivo has been shown to increase retinal vascular permeability (RVP). This study examines whether Ca–I also has an impact on other markers for early diabetes associated retinal dysfunction such as increased retinal leukostasis and electrophysiological abnormalities.
Intravitreal injections (10µL) of CA–I (200ng), CA–I + acetazolamide (10µM), or balanced saline solution (BSS) were performed under sterile conditions in male Sprague–Dawley rats. At 1 or 48 hours post injection, leukocyte adhesion was assessed by acridine orange (1mg/kg in sterile saline) infusion. Static leukocytes were imaged by scanning laser ophthalmoscope at 20 minutes post infusion and quantified across 9 quadrants. Electroretinograms (ERG) (single white flash, 1.4x10^4 ftc, 5 ms) were obtained from both eyes after 1 hour of dark adaptation.
Intravitreal CA–I did not effect leukostasis at 1 hour after injection. At 48 hours post injection, CA–I induced a 3–fold increase in retinal leukostasis compared to BSS treated eyes (13.8±4.5 vs 4.4±1.6 cells/pixel2, p<0.001). The increase in retinal leukostasis by CA–I was inhibited with co–injection with acetazolamide (4.8±1.3, p<0.001). The injection of Ca–I shortened implicit time for the a–wave by 8%(7.8±0.4 vs 8.5±0.4 ms, p=0.011) compared to contralateral BSS treated eyes. Similarly, oscillatory potentials (OP)implicit times were shortened for OP2 (4.7%, p=0.047), OP3 (4.3%, p=0.023), and OP4 (4.0%, p=0.03) versus BSS control. Signal amplitudes were not significantly affected, however, increases were observed for OP3 (20%) and OP4 (38%)amplitudes.
CA–I induces retinal leukocyte adhesion after 48 hours. The effect is blocked by acetazolamide indicating a possible role for Ca and retinal inflammation. Changes in electrophysiology suggest that Ca–I may effect ocular acid base regulation and alter neuronal polarization.
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