gramicidin-a and Corneal-Injuries

Previous work from our laboratory and others has shown that, in some epithelia, the epithelial sodium channel (ENaC) increases its expression during wound healing. In these cases, inhibition of the channel determines a decrease in the healing rate, a result suggesting a role for ENaC in the overall healing process. To understand further this role of ENaC in epithelia, we explored the participation of ENaC in wound healing in four cultured epithelial cell lines selected on the basis of their different embryonic origins, function and modality of healing, i.e., by lamellipodial cell crawling or by actin cable formation. Three of the cell lines (bovine corneal endothelial cells, rabbit corneal epithelial cells and Madin-Darby canine kidney cells) exhibited an increase in ENaC expression and consequent membrane potential depolarization and an increase in cytosolic sodium and calcium, whereas one line (bovine aortal endothelial cells, BAEC) did not exhibit any of these changes. In all of the cell lines, however, ENaC inhibition determined a similar decrease in the rate of wound healing. In BAEC monolayers, the increase in ENaC activity produced plasma membrane depolarization, increased cytosolic sodium and calcium, and augmented the velocity of healing. These novel findings contribute to the idea that ENaC plays a critical role in wound healing in various epithelia, independently of the modality of healing and of any increase in the expression of the channel.

Topics: Animals; Anti-Bacterial Agents; Aorta, Thoracic; Cattle; Cell Line; Colforsin; Cornea; Corneal Injuries; Dogs; Epithelial Cells; Epithelial Sodium Channel Blockers; Epithelial Sodium Channels; Epithelium; Gramicidin; Madin Darby Canine Kidney Cells; Membrane Potentials; Rabbits; Vasodilator Agents; Wound Healing

The eight topical antibiotic solutions that we use most frequently were tested for their effect on corneal epithelial wound healing in the rabbit. Five percent cefazolin sodium and a mixture of neomycin sulfate, polymyxin B sulfate, and gramicidin (Neosporin) had the least effect on epithelial healing rates and quality of healing, 10% sulfacetamide sodium and an artificial tear had intermediate effects, and gentamicin sulfate, tobramycin, and chloramphenicol were the most toxic. No substantial differences were found between gentamicin and the newer aminoglycoside, tobramycin, and the "fortified" preparations of these two drugs did not seem to be more toxic than the 0.3% solutions. Therefore, topical antibiotic solutions vary in their effects on the corneal epithelium, and not all antibiotics should be considered innocuous when used in the treatment of epithelial defects.

Topics: Administration, Topical; Animals; Anti-Bacterial Agents; Cefazolin; Corneal Injuries; Epithelium; Female; Gramicidin; Male; Neomycin; Ophthalmic Solutions; Polymyxin B; Rabbits; Wound Healing

Topics: Administration, Topical; Animals; Atropine; Cornea; Corneal Injuries; Dexamethasone; Disease Models, Animal; Gramicidin; Male; Neomycin; Parasympatholytics; Phenylephrine; Polymyxins; Rabbits; Wound Healing