ABSTRACT
@#【Objective】To test the hypothesis that inhibiting sodium absorption via the epithelial sodium channel（ENaC） will increase ocular hydration and cure the rabbit′ s dry eye induced by scopolamine. 【Methods】In the experiment，24 New Zealand rabbits weighing about 2.0- 2.5 kg were divided into 3 groups：tested group（8 rabbits）， control group （8 rabbits），and treatment group （8 rabbits）. For the rabbits in the tested group，they were given subcutaneous injection of scopolamine 4 times a day for 12 consecutive days to induce the dry eye. For the rabbits in the control group，they accepted subcutaneous injection of saline solution. For the rabbits in the treatment group ，they were firstly given the same treatment as the rabbits in the tested group. Then，the local regions in their right eyes received the application of 100 mmol/L amiloride （a sodium channel inhibitor）. Meanwhile，the local regions in their left eyes received the application of equivalent saline solution. We detected ENAC α and ENAC γ subunits of epithelial sodium channel in conjunctival epithelium by fluorescence quantitative PCR and detected the opening of epithelial sodium channel by short- circuit current technology. Finally，we compared the ENaC α and ENaC γ gene expression，corneal fluorescein sodium staining and tear secretion among the 3 groups. Fluorescence quantitative PCR was used to detect ENaC α and ENaC γ subunits of epithelial sodium channel in conjunctival epithelium and short-circuit current was used to detect the opening of epithelial sodium channel. The ENaC α and ENaC γ gene expression，corneal fluorescein sodium staining and tear secretion （immerged length） were compared among 3 groups.【Results】 The results showed that the quantity of tear secretion was（17.00 ± 0.37）mm for the control group，（4.42 ± 1.34）mm for the tested group（P<0.001 vs Control，n=8） and（14.25 ± 0.54）mm for the treatment group（P>0.05 vs Control，n=8）. The results of short-circuit current detection showed that the sodium current was（5.72 ± 0.35）μA /cm2 in normal model and（12.24 ± 0.54）μA /cm2 in dry eye model（P<0.001）. After Amiloride treatment，the sodium current decreased to（4.00 ± 0.61）μA/cm2 （P>0.05） and there was no statistical difference compared with the normal group. According to the results of fluorescence quantitative PCR，the expression of ENaC α and ENaC γ subunits and IL- β in in dry eye model were up-regulated（P<0.01） compared with that in normal group. After topical amiloride application，there were no statistical differences in inflammatory cytokines IL- 1 β，ENaC α，and ENaC γ between the normal group and treatment group（P>0.05，n=8）. After treatment，tear secretion increased （P<0.001），and ocular surface staining improved significantly.【Conclusion】 Topical application of amiloride increase the quantity of preocular tears owing to inhibition of conjunctival sodium channels and could provide an effective new therapy for chronic dry eye.