Aim
To measure the expression of transient receptor potential cation channel subfamily V member 4 (TRPV4) in the rat cornea and determine whether it is related to adenosine triphosphate (ATP) generation in a rat model of acute ocular hypertension (AOH).
Conclusion
The ATP concentration in the AOH rat cornea is increased by TRPV4 activation.
Methods
Immunofluorescence staining of TRPV4, P2X2 receptor, P2X3 receptor, and β3-tubulin in rat corneal longitudinal sections and paved was performed to clearly display histological structures. Rat models of AOH and agonist/antagonist-treated groups were established and corneal ATP was measured using an ATP assay. The independent t-test and simple linear correlation model were adopted for statistical analyses.
Results
Immunofluorescence staining of rat cornea sections revealed that epithelial and endothelial membranes showed strong immunoreactivity for TRPV4 and P2X2 receptor and coexpression with β3-tubulin in the rat corneal epithelial layer. Corneal ATP was significantly higher in the AOH rat model than in the control (P<0.05) and apparently lower after pretreatment by applying eyedrops of TRPV4 antagonist RN1734 with 30-40 mm Hg intraocular pressure (IOP; P<0.05). A simple linear regression model showed a positive correlation between rat corneal ATP and IOP values (R 2=0.996, P=0.0134) from the normal IOP (113 mm Hg) to 40 mm Hg. At 10-40min after anterior chamber injection of GSK1016790A (0.01 mL, 50 nmol/L in 0.9% NaCl), corneal ATP was significantly higher than in the control group (P<0.05), which peaked at 10min. The ATP concentration of the normal epithelium was higher than that of the endothelium in the AOH rat model and after anterior chamber injection of GSK1016790A (P<0.05).