The effect of diamide on lens glutathione and lens membrane function.

TLDR: The observed membrane changes suggest the presence of certain sidfhydryl groups on the lens membrane which are unusally susceptible to oxidation when the GSH level is precipitously reduced, and GSH would be necessary to maintain these —SH groups in the reduced form for proper membrane function.

Abstract: The physiological role of glutathione (GSH), present in exceptionally high concentration in the lens, has never been clearly delineated. Using Rb we have studied the cation transport and permeability of rat leiises incubated in vitro with diamide, a relatively specific intracellular GSH oxidant. Lenses incubated without glucose ivith 0.4 mM. diamide manifest a progressive decrease in GSH with time. In the presence of glucose this effect is minimized, presumably because the GSH level is maintained by the NADPH generated by the pentose shunt mechanism. When lenses are preincubated with diamide without glucose for 2 hours, a 55 to 57 per cent decrease in Rb uptake is observed. In addition, diamide also effects a 53 per cent increase in the Rb run-out of lenses incubated without glucose. In the presence of glucose both of these effects are minimized. Incubation with dithioihreitol leads to a small but definite increase in the Rb uptake of diamide-treated lenses. The observed membrane changes suggest the presence of certain sidfhydryl groups on the lens membrane which are unusally susceptible to oxidation when the GSH level is precipitously reduced. These membrane —SH groups are involved in cation pumping (Rb uptake) as well as in determining the degree of membrane permeability (Rb run-out). GSH would be necessary to maintain these —SH groups in the reduced form for proper membrane function.