Abstract
Abstract: :
Purpose: Aquaporin-1 (AQP1) is a hexahelical integral membrane protein that functions as a regulated channel for water and cations in fluid transporting tissues, including many in the eye. While AQP1 has been cloned from a cDNA library prepared from retinal pigment epithelium (RPE) isolated from human fetal tissue, three separate studies failed to detect AQP1 protein in adult human or adult rat RPE preparations using various immunochemical techniques. The purpose of this study was to specifically examine the expression of AQP1 in adult human RPE in situ and in cells isolated from human eye bank eyes using alternative methodologies. Methods: RPE tissue was harvested for biochemical analyses after solubilization in SDS sample buffer or RPE cells were harvested for growth in culture. Cultured RPE were maintained at least two weeks at confluence then whole cell lysates were prepared. Lysates were analyzed for AQP1 expression by western blot analysis using an affinity-purified anti-AQP1 IgG preparation. Results: We observed only two immunoreactive bands, characteristic of the glycosylated 40-60kd and the unglycosylated 28kd forms of AQP1 in each human RPE in situ preparation and cell line tested. AQP1 expression in the four cell cultures examined varied considerably and appeared to correlate positively with its degree of epithelial morphology. Conclusion: These results demonstrate the expression of AQP1 protein in adult human RPE and implicate a role for AQP1 in transepithelial fluid movement across the RPE.
Keywords: 567 retinal pigment epithelium • 533 pump/barrier function