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NaCl osmotic perturbation can modulate hydration control in rabbit cornea
Jeffrey W Ruberti1, Stephen D Klyce
1Department of Biomedical Engineering, Tulane University, New Orleans, LA, USA. jeff@campoly.com
Experimental Eye Research
|February 8, 2003
Summary
The corneal endothelium rapidly controls stromal hydration in response to small NaCl osmotic changes, but this effect is not reversible. This mechanism helps regulate corneal thickness and hydration homeostasis.
Area of Science:
- Ophthalmology
- Physiology
- Biophysics
Background:
- The corneal endothelium maintains corneal hydration through active solute transport.
- Control mechanisms for this active transport system are not well understood.
Purpose of the Study:
- Investigate corneal response to small NaCl osmotic perturbations.
- Identify response signatures of transport control using advanced thickness measurement.
Main Methods:
- Adult rabbit corneas were mounted in perfusion chambers with isolated endothelium.
- Endothelial perfusate was altered by +/-15 mOsm or +/-45 mOsm NaCl.
- Stromal thickness was monitored using an automatic scanning specular microscope.
- Transport coefficients were determined using a numerical model of corneal hydration dynamics.
Main Results:
- Small NaCl perturbations (+/-15 mOsm) induced a rapid, non-reversible stromal volume control response.
- Hypotonic perturbation led to sustained thinning (14 µm); hypertonic perturbation led to swelling (16 µm).
- Model calculations suggested a persistent 26% reduction in passive endothelial NaCl permeability after perturbation.
- Larger perturbations (+/-45 mOsm) did not consistently elicit a similar response.
Conclusions:
- Trans-endothelial fluid transport is rapidly modulated to control stromal hydration under small NaCl osmotic stress.
- This modulation cushions osmotic shock and reduces corneal thickness changes.
- The observed response is not short-term reversible and may contribute to corneal hydration homeostasis.