Abstract
Purpose: :
The retinal pigment epithelium (RPE) maintains attachment of the retina by moving fluid from the subretinal space to the choroid. Fluid accumulation in the subretinal space in pathologies such as macular edema and central serous chorioretinopathy can result in retinal detachment. Since Atrial Natriuretic Peptide (ANP) has been shown to influence fluid transport in various epithelia the goal of this project was to determine the role of ANP in fluid transport across human retinal pigment epithelium.
Methods: :
Primary human retinal pigment epithelial cells were cultured on 0.45um Millicell nitrocellulose filters for 6-8 weeks according to the method of Hu et. al. 2000. The change in volume of media on the apical side of RPE monolayers was used to determine the direction and rate of fluid movement (uL/hr/cm2) during 2 hour treatment periods at 37°C. First we established baseline fluid transport across individual monolayers using media alone. Next we determined the effects of 4.5uM ANP in the presence or absence of 45uM Anantin, a Natriuretic Peptide Receptor-specific antagonist.
Results: :
RPE monolayers displayed an average net transepithelial resistance of 370 Ω*cm2. Compared to the baseline flow rate (-0.63 + 3.08 uL/hr/cm2, n = 14), treatment of RPE monolayers with ANP (4.5uM) significantly increased the apical to basal flow rate (12.76 + 4.09 uL/hr/cm2, n = 14, p<0.0001). Anantin (45µM) significantly inhibited the ANP stimulated fluid transport (5.19 + 4.19 uL/hr/cm2, n = 9, p<0.02).
Conclusions: :
Atrial Natriuretic Peptide stimulates fluid transport across the RPE in the apical to basal direction. Specific blockage of ANP stimulation by Anantin indicates the involvement of Natriuretic Peptide Receptor in RPE fluid transport.
Keywords: retinal pigment epithelium • receptors: pharmacology/physiology • retinal detachment