title: Evaluation of acute corneal barrier change induced by topically applied preservatives using corneal transepithelial electric resistance in vivo.
abstract: OBJECTIVE
  We evaluated acute changes in corneal barrier function after instillation with preservatives using corneal transepithelial electric resistance (TER) in vivo and cytotoxicity tests in vitro.
  
  
  METHODS
  The corneal TER of live rabbits was measured using a volt-ohm meter and silver/silver chloride electrodes. The cornea was exposed to the preservatives benzalkonium chloride (BAC; 0.001%, 0.002%, 0.005%, 0.01%, and 0.02%), 0.04% paraben, 0.5% chlorobutanol, 0.005% chlorhexidine digluconate, 2% boric acid, and 0.01% ethylenediaminetetraacetic acid, and then changes in the TER were monitored for 60 seconds. Cultured normal rabbit corneal epithelial cells were exposed to the same preservatives for 60 seconds in vitro, and cell viability was evaluated using the WST-1 assay.
  
  
  RESULTS
  The TER instantly decreased and became significantly lower than the control within 10 seconds after instillation with 0.01% and 0.02% BAC (P < 0.01) and within 60 seconds after that with 0.005% BAC (P < 0.01). The TER decreased concomitantly with increasing BAC concentration. Cell viability after instillation with 0.005%, 0.01%, and 0.02% BAC for 60 seconds was significantly lower than that of the control (P < 0.0001). None of the other preservatives significantly altered the TER or cell viability. Decreases in the TER correlated with cell viability (r = 0.94, P < 0.0001).
  
  
  CONCLUSIONS
  Instillation with BAC immediately disrupted the corneal epithelium. Corneal epithelial cell death is supposed to be associated with a decline in barrier function; thus, corneal TER measurement in vivo can assess the acute toxicity of preservatives added to ophthalmic drugs.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki City, Nagasaki, Japan. maok@nagasaki-u.ac.jp
authors.forename: Mao
authors.initials: M
authors.lastname: Kusano
authors.forename: Masafumi
authors.initials: M
authors.lastname: Uematsu
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kumagami
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sasaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Kitaoka
mesh_terms: D000287:Administration, Topical; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D017097:Electric Impedance; D019573:Epithelium, Corneal / Q000187:drug effects* / Q000473:pathology; D008297:Male; D011310:Preservatives, Pharmaceutical / Q000633:toxicity*; D011817:Rabbits; D019108:Tight Junctions / Q000187:drug effects*
chemical_list: D011310:Preservatives, Pharmaceutical