Metal ion catalyzed liquefaction of vitreous by ascorbic acid: role of radicals and radical ions.

The effect of Fe2+ and Cu2+ on the intact calf vitreous in the presence or absence of exogenous ascorbic acid was investigated in vitro. Liquefaction of vitreous gel was evident in the presence of either ion. The loss of gel structure was greater in the presence of exogenous ascorbic acid than in its absence. As shown by high-performance liquid chromatography, liquefaction was accompanied by depolymerization of vitreous hyaluronic acid which is degraded by .OH, generated by the metal ion catalyzed oxidation-reduction system. The involvement of .OH in this process was also evident from the significant reduction in liquefaction in the presence of the .OH-specific scavenger mannitol.