Is it possible to maintain a normal glutathione level in lenses in vitro?
In most types of experimentally induced cataracts, glutathione (GSH) content decreases considerably before the onset of opacity. GSH may provide a protective function for protein SH groups by scavenging oxidative products that may impair lens metabolism. To avoid impairment of lens metabolism by decreased levels of GSH it may be possible in vitro: (1) to stimulate GSH synthesis by enrichment of the incubation medium with the amino acids necessary for GSH synthesis or (2) to enrich the incubation medium with the tripeptide itself so that it can be taken up by the lens. Both approaches were investigated with bovine lenses. Lenses were incubated in pairs in a salt solution without carbohydrates, so as to deplete lens of GSH. Following starvation, one lens of each pair was incubated for recovery in TCM 199 enriched with MgSO4 and the three amino acids of GSH; the other lens was put into a freshly prepared salt solution. After 6 h, lenses from the recovery solution contained more GSH than the other lenses. Addition of fructose-1,6-diphosphate to the medium enhanced this effect. When, after starvation, lenses were incubated in the presence of different amounts of GSH, GSH lens content rose, with the highest in those lenses incubated in a medium with a final molarity of 4 X 10(-3) M GSH. Therefore, incubation of lenses depleted of GSH in medium with either the amino acids of GSH or GSH itself appear to facilitate recovery of GSH content.