Proton nuclear magnetic resonance study on the barrier function of pig corneal epithelium and endothelium

Using gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) as a tracer, the barrier function of the corneal epithelium and endothelium was evaluated by proton nuclear magnetic resonance. Whole pig eyes and cornea excised with scleral rim, which had been incubated in dextran-added Gd-DTPA solution, were subjected to T1 relaxation measurement and magnetic resonance imaging (MRI). After incubation, the T1 relaxation rate (1/T1) of the excised cornea increased to a steady value, whereas that of the cornea from the whole eye increased only slightly. These results indicated that the increase in the T1 relaxation rate of the excised cornea attributable to Gd-DTPA penetration from the corneal endothelium and that the corneal epithelium exhibited a strong barrier function against Gd-DTPA entry. The MRI study also confirmed the strong barrier, enhanced signals being detected within the aqueous fluid in the T1-weighted image only when the corneal epithelium was abraded. Since Gd-DTPA scarcely penetrates the intact corneal epithelium, Gd-DTPA-enhanced MRI shows potential as a quantitative tracer in evaluating epithelial barrier disruption.