Comparison of intraocular solutions on glycolysis and levels of ATP and glutathione in the retina

The Disposition and Bioavailability of35S-GSH from35S-GSSG in BSS PLUS®in Rabbit Ocular Tissues

The purpose of this study was to evaluate the biodistribution and uptake of 35S-GSH into intraocular tissues following the administration of BSS PLUS containing 35S-GSSG by either an anterior chamber or intravitreal injection. This study evaluated the disposition and uptake of the 35S-radiolabel, the intracellular concentrations of 35S-GSH from extracellular 35S-GSSG, and the percentage of 35S-GSH to the total cellular GSH pool. Glutathione was analyzed by high-performance liquid chromatography (HPLC) using fluorescence detection after derivitizing the thiols in situ with monobromobimane. The effluent from the GSH peak was then collected for measurement of 35S-GSH. After an anterior chamber injection of 35S-BSS PLUS, 35S-radioactivity rapidly disappeared from the aqueous humor between 0.5 and 2 hours; corneal 35S-radioactivity remained constant over time. 35S-GSH was detected in the iris and ciliary body. However, in the cornea, 35S-GSH became the predominant radioactive thiol in the stroma, endothelium, and epithelium; the corneal stroma appeared to be a possible GSH reservoir for the adjacent corneal layers. After an intravitreal injection, 35S-radioactivity slowly decreased in the vitreous humor but was readily taken up by the tissues of the posterior segment, especially the retina and choroid, which showed the greatest concentrations of 35S-GSH of all tissues studied. The data from this study demonstrate that 35S-GSSG in BSS PLUS is metabolized and taken up by ocular cells and that 35S-GSH becomes incorporated into the intracellular GSH pool of ocular tissues.

The effects of different intraocular irrigating solutions on the apoptosis of cultured RPE cells

PURPOSE

To investigate the effect on porcine retinal pigment epithelial (RPE) cells of modified intraocular irrigating solutions compared with BSS and BSS plus.

METHODS

Confluent cultures of RPE cells were incubated in experimental intraocular irrigating solutions. The cells were then examined for breakdown of DNA by the TUNEL procedure. Fragmentation of the DNA from cells was also confirmed by flow cytometry.

RESULTS

Most of the experimentally, treated cells exhibited a shrunken appearance for up to 72 h. There was a steady increase in the number of cells labeled by the TUNEL method in three solutions with time. The data demonstrated that the influence of solutions on the percentage of RPE cell nuclei that gave a clear positive TUNEL stain was, in ascending order: modified solution>BSS>BSS plus. Of the three solutions tested, BSS plus showed least apoptosis.

CONCLUSIONS

It is suggested that BSS plus is less harmful to RPE cells than the other solutions tested. Introduction of other adjunctive solutions of antibiotics, mydriatics, miotics, and steroid, resulting in an altered electrolyte balance, pH, or osmolality in the solution, may compromise the safety and efficacy of a properly formulated and packaged solution.

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 x 10(-6) cm/s on average) than Krebs-Ringer solution or Opeguard (1.9 or 1.8 x 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 x 10(-6) cm/s v 2.0 x 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.