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B. Reid, A. C. Vieira, M. J. Mannis, I. Schwab, M. Zhao; Selective Probe Measurement of Ion Flux in Rat Cornea Wounds. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6292.
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The corneal epithelium has multiple functions including mechanical protection from pathogens and refraction of light onto the lens and retina. It also contributes to the maintenance of corneal transparency. The integrity of the epithelial surface is necessary for normal vision. Fortunately most corneal epithelial wounds are repaired promptly. Many factors play a role in epithelial cell migration and wound healing, such as chemotaxis, haptotaxis and contact guidance. Previous studies have shown the important role of endogenous wound-induced electric fields in corneal wound healing. When a wound occurs in the corneal epithelium, a lateral electric field is generated, which stimulates epithelial cell division and migration into the wound bed. The purpose of this study was to look at single ion flux at rat corneal wound edges to determine which ions specifically contribute to the wound electric current. By defining the electrophysiological properties of the cornea, we will be able to understand the mechanisms of the endogenous wound electric fields and offer new approaches to manage corneal injury and/or disease.
Using an ion-selective microelectrode system (kindly loaned by Dr. Ebenezer Yamaoh, Department of Otolaryngology, UC Davis), the flux of specific ions (sodium, chloride, calcium, and hydrogen to measure pH) into or out of rat cornea wounds was measured for up to 90 min after wounding.
After wounding, there was a small efflux of sodium which declined to almost zero during the first 30 min. Calcium efflux was larger and persisted for at least 90 min. In contrast, there was an influx of chloride ions which steadily increased for 90 min. There was a substantial decrease in pH at the wound edge.
The outward electrical current we have measured previously in cornea wounds appears to be carried in part by an outward flow of calcium ions and an inward flow of chloride ions. Surprisingly, sodium ions do not seem to play an important role.
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