title: The effect of topical amiloride eye drops on tear quantity in rabbits.
abstract: OBJECTIVE
  To investigate the presence of epithelial sodium channels (ENaC) in rabbit and human conjunctival epithelium and to test the effects of topical amiloride, a potassium-sparing diuretic that blocks the ENaC, on tear quantity in rabbits.
  
  
  METHODS
  Both healthy normal human and rabbit conjunctival tissues underwent immunohistochemistry staining for ENaC-α and γ subunits as well as for reverse transcription-polymerase chain reaction (RT-PCR) for detection of ENaC-α and ENaC-γ subunit mRNA expression. Rabbits were instilled topical amiloride eye drops and tear function tests were performed before and after instillations.
  
  
  RESULTS
  Immunohistochemical staining for ENaC-α subunit in all rabbit eyes showed positive staining in apical and basal conjunctival epithelial cells. Human conjunctival epithelia revealed positive staining with ENaC-α antibody especially in the apical and basal layers. Immunohistochemistry staining with ENaC- γ antibody also revealed positive staining of the conjunctival epithelial cells especially in the basal layers. The ENaC-α mRNA was detected in samples from healthy white rabbit conjunctival epithelia, and ENaC-α and ENaC- γ mRNAs were detected in samples from healthy human conjunctival epithelia. The mean tear quantity showed a significant increase at 15 and 30 min compared to the pre-instillation value in eyes assigned to amiloride eye drops. The mean tear quantity at 15 and 30 min was significantly higher in the amiloride group compared to the control eyes.
  
  
  CONCLUSIONS
  Topical amiloride application appears to increase the quantity of preocular tears owing to inhibition of conjunctival epithelial sodium channels.
authors.affiliation: Social Insurance Chukyo Hospital, Department of Ophthalmology, Nagoya, Japan.
authors.forename: Shuya
authors.initials: S
authors.lastname: Hara
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hazama
authors.forename: Masao
authors.initials: M
authors.lastname: Miyake
authors.forename: Takashi
authors.initials: T
authors.lastname: Kojima
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Sasaki
authors.forename: Jun
authors.initials: J
authors.lastname: Shimazaki
authors.forename: Murat
authors.initials: M
authors.lastname: Dogru
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tsubota
mesh_terms: D000287:Administration, Topical; D000584:Amiloride / Q000008:administration & dosage* / Q000494:pharmacology*; D000818:Animals; D003228:Conjunctiva / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism; D005260:Female; D019793:Fluorescein / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D009883:Ophthalmic Solutions / Q000008:administration & dosage* / Q000494:pharmacology*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013194:Staining and Labeling; D013666:Tears / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D053503:Epithelial Sodium Channels; D009883:Ophthalmic Solutions; D021122:Protein Subunits; D012333:RNA, Messenger; D000584:Amiloride; D019793:Fluorescein