Purpose. Corneal endothelial fluid transport is dependent on HCO3- and CO2 fluxes. CO2 permeability (PCO2) measurements in an oocyte expression system and in reconstituted proteoliposomes have suggested that the water channel AQP1 can transport CO2. An AQP1 knockout mouse model, however, showed no evidence for CO2 transport through AQP1 in erythrocytes or lung. Because HCO3- and CO2 fluxes are essential to endothelial function, the current study was conducted to determine whether AQP1 expression levels in confluent cultures of bovine corneal endothelial cells (BCECs) affects membrane PCO2. Methods. BCEC endogenous AQP1 expression was reduced by antisense oligonucleotide (AO) transfection or adenoviral antisense-AQP1 (AV) infection. AQP1 was overexpressed by adenoviral sense-AQP1 (SV) infection, which directs expression of recombinant AQP1. Results. Expression of AQP1 and osmotic water permeability (control Pf = 0.046 ± 0.005 cm/sec) were reduced 45% and 36.5%, respectively, by AO transfection and reduced 67% and 49%, respectively, by AV infection. SV infection induced a more than threefold overexpression of AQP1 but showed only a 37% increase in Pf. Adenoviral empty virus (EV) infection did not change AQP1 expression or Pf. PCO2 was determined by measuring the rate of intracellular pH decrease after exposure to CO2/HCO3--rich solutions, as measured by the pH-sensitive fluorescent dye 2′,7′-bis-(2-carboxyethyl)-5-(and-6)-carboxy-fluorescein (BCECF). Apparent PCO2 of BCEC (0.0036 ± 0.00023 cm/sec) was not different among control, oligonucleotide-transfected, and adenoviral-infected cells. Pf could also be reduced more than 50% by 3 to 5 minutes' exposure of control cells to 0.5 mM p-chloromercuriphenylsulfonic acid (pCMBS), but this had no effect on rates of intracellular pH decrease. Conclusions. AQP1 does not contribute to PCO2 in corneal endothelial cells.
|Original language||English (US)|
|Number of pages||7|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - 2001|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience