Intraocular irrigating solutions and barrier function of retinal pigment epithelium

AIM—To study the effect of intraocular irrigating solutions on the barrier property of the retinal pigment epithelium (RPE).
METHODS—The isolated rabbit RPE-choroid mounted on Ussing-type chambers under short circuit conditions was used. According to a previous study, the inward (from the choroid to the vitreous side) permeability of the tissue to carboxyfluorescein was adopted as a quantitative index of the barrier function of the RPE cells.
RESULTS—Of the three solutions tested, Krebs-Ringer solution, a commercially available glucose glutathione bicarbonate solution (BSS plus), and glucose citrate-acetate bicarbonate solution (Opeguard), BSS plus gave a significantly lower permeability (1.1 × 10^-6 cm/s on average) than Krebs-Ringer solution or Opeguard (1.9 or 1.8 × 10^-6 cm/s on average, respectively) (unpaired t test with Bonferroni's correction, p<0.05). Since the major chemical difference between BSS plus and the other two solutions is the incorporation of oxidised glutathione (GSSG), the effects of GSSG were studied using solutions having an identical composition to BSS plus, but with various concentrations of GSSG. The solution containing 0.3 mM GSSG gave significantly lower permeability than that without GSSG (1.1 × 10^-6 cm/s v 2.0 × 10^-6 cm/s) (unpaired t test with Bonferroni's correction, p<0.05).
CONCLUSION—It was suggested that BSS plus is less harmful to the barrier function of the RPE cells and that GSSG has a beneficial effect on its maintenance.