Endothelial pump function in rabbit corneas kept under eye bank conditions

Area of Science:

• Ophthalmology
• Cell Physiology
• Biomedical Engineering

Background:

• The corneal endothelium maintains corneal clarity through active fluid transport.
• Understanding endothelial pump function is crucial for eye banking and transplantation.

Purpose of the Study:

• To quantify the endothelial pump rate in rabbit corneas under eye bank conditions.
• To assess the effect of ouabain, an inhibitor of the Na+/K+-ATPase, on corneal hydration.

Main Methods:

• Corneal swelling rates were measured in the presence and absence of ouabain.
• Endothelial pump activity was calculated based on weight changes over time.
• Fluid transport was normalized to corneal stroma weight and thickness.

Main Results:

• Control corneas maintained stable weight for one week.
• Ouabain-treated corneas showed continuous swelling, increasing by 41% of initial weight in 24-48 hours.
• This equates to an endothelial pump activity of 2.3% of stroma weight per hour (9 microns/hour).
• Individual endothelial cells pumped 200-300% of their volume per hour between days 1 and 8.

Conclusions:

• The corneal endothelium exhibits significant active fluid transport crucial for maintaining corneal deturgescence.
• Ouabain effectively inhibits this pump, leading to rapid corneal edema.
• Endothelial pump activity gradually declines after 8 days but does not fully cease.