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Paracellular ionic and transcellular water diffusions across rabbit corneal endothelium.
1Department of Optometry, University of Wales Institute of Science and Technology, Cardiff.
The Journal of Physiology
|April 1, 1987
Summary
Corneal endothelial cells primarily allow ion diffusion via the paracellular route, not transcellularly. Water transport across the endothelium is mainly transcellular, with high diffusional permeability.
Area of Science:
- Ophthalmology
- Corneal Physiology
- Cell Biology
Background:
- The corneal endothelium regulates ion and water transport, crucial for corneal clarity.
- Understanding transport pathways is key to managing corneal edema and disease.
Purpose of the Study:
- To elucidate the primary pathways for ion and water diffusion across the corneal endothelium.
- To quantify the electrical resistance of the corneal endothelial monolayer and individual cell membranes.
Main Methods:
- Intracellular microelectrode measurements to estimate corneal endothelial cell membrane electrical resistance.
- Measurement of endothelial monolayer electrical resistance.
- Comparison of endothelial and stromal ion and water permeability.
Main Results:
- Corneal endothelial cell membrane resistance is approximately 400 MΩ.
- Measured endothelial monolayer resistance is 12.7 ± 0.8 Ω cm², indicating ~99% of ion diffusion occurs paracellularly.
- Endothelial water diffusional permeability is significantly higher than stromal permeability and largely unmeasurable.
Conclusions:
- Ion diffusion across the corneal endothelium predominantly occurs through the paracellular pathway.
- Water transport across the corneal endothelium is primarily transcellular.
- The distinct permeability characteristics of the endothelium are vital for corneal hydration homeostasis.