Stromal sodium binding after glycosaminoglycan digestion

Area of Science:

• Ophthalmology
• Biochemistry
• Materials Science

Background:

• Corneal stroma is primarily composed of collagen and glycosaminoglycans (GAGs).
• GAGs, such as hyaluronic acid, play a crucial role in corneal hydration and structural integrity.
• The binding of ions, like sodium, to corneal components influences stromal swelling and mechanical properties.

Purpose of the Study:

• To quantify the contribution of glycosaminoglycans to sodium binding in rabbit corneal stroma.
• To determine the proportion of bound sodium associated with non-saccharide binding sites within the corneal stroma.

Main Methods:

• Isolated rabbit corneal stroma was hydrated and treated with testicular hyaluronidase to digest GAGs.
• Sodium and chloride content of normal and treated stroma were measured after equilibration with saline.
• Donnan equilibrium principles were applied to calculate bound sodium content.

Main Results:

• Normal corneal stroma contained approximately 200 mEq. bound sodium per kilogram of dry weight.
• Hyaluronidase-treated stroma showed a reduced bound sodium content of about 110 mEq. per kilogram of dry weight.
• These results indicate that roughly half of the bound sodium in the corneal stroma is associated with non-GAG binding sites.

Conclusions:

• Glycosaminoglycans account for only about half of the bound sodium in the corneal stroma.
• Non-saccharide binding sites contribute significantly to the ionic composition and hydration of the corneal stroma.
• Understanding these binding characteristics is essential for comprehending corneal biomechanics and developing therapeutic strategies.