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D. J. Calkins, R. Roberts, M. Gradianu, B. A. Berkowitz; Manganese-Enhanced MRI Studies of Intraretinal Ionic Activity in the DBA/2J Mouse Model of Glaucoma. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2878.
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Manganese-enhanced MRI (MEMRI) is a powerful non-invasive approach for studying intraretinal ionic regulation in vivo in models of ocular injury, diabetic retinopathy, retinopathy of prematurity or choroidal melanoma. In this study, we tested the hypothesis that manganese-enhanced MRI (MEMRI) is a sensitive approach for non-invasively and quantitatively measuring in vivo age-related changes in the regulation of intraretinal ion activity in the DBA/2J mouse model of pigmentary glaucoma.
Four hours post i.p injection of 66 mg/Kg MnCl2, high resolution MEMRI data were collected from light-adapted 3 mo C57BL/6 (n = 4) and DBA/2J (n = 9) mice, and 10 mo C57BL/6 (n = 7) and 11 month DBA/2J (n = 6) mice. Intraretinal ion activity, together with central retinal thickness and ocular circumference were measured from the MEMRI data. Eyes and optic nerves were harvested for histological comparisons.
As C57BL/6 mice aged, ocular circumference increased 3% (p < 0.05), and total central retinal thickness decreased about 8% (p 0.05). In addition, inner and outer retinal uptake of manganese increased (p 0.05). In contrast, as DBA/2J mice aged, circumference increased 15% (p < 0.05), and both total and inner retinal thickness significantly decreased 7% and 8% (p 0.05). However, the activity difference between inner and outer retina at 3 mo (14%) was significantly different from that at 11 mo (3%). This was largely due to a 6% decrease in inner retinal manganese uptake.
Using MEMRI, we readily detected differences in the age-dependent progression of changes in ocular circumference, retinal thickness and intraretinal ion activity between C57BL/6 and DBA/2J strains. Detection of changes in key ocular parameters in the DBA/2J mouse highlights MEMRI as a powerful tool for measuring correlations in structural and functional ocular responses to glaucomatous stressors in vivo.
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