Partial reversal of methylprednisolone-induced opacity in isolated rat lenses

We examined whether opacity is reversed in isolated rat lenses with opacities of different grades induced by methylprednisolone treatment by withdrawal of the steroid treatment. Transparent lenses isolated from male Wistar rats aged 6 weeks were incubated in TC-199 medium containing methylprednisolone hemisuccinate (1.5 mg/ml) for 24 or 48 h to induce opacities of two different grades (one was a slight cortical opacity around the equator and the other a heavy cortical opacity spreading from the equator to the cortex). In the slightly opaque lenses, water content was preserved at the level of transparent lenses untreated with steroid, although a 3.2-fold increase in Na(+)/K(+) ratio and a 20% decrease in Na(+),K(+)-ATPase activity were observed. In contrast, in the heavily opaque lenses, a significant increase in water content was accompanied by a 31.0-fold increase in Na(+)/K(+) ratio and a 27% decrease in Na(+),K(+)-ATPase activity. When the slightly and heavily opaque lenses were further incubated in steroid-free medium for 24 or 48 h, a partial opacity reversal was found in the slightly opaque lenses, but not in the heavily opaque lenses. In the slightly opaque lenses incubated in steroid-free medium for 48 h, increased Na(+)/K(+) ratio and decreased Na(+),K(+)-ATPase activity were restored to nearly the levels of untreated transparent lenses. Incubation of the heavily opaque lenses in steroid-free medium for 48 h caused further slight increases in water content and Na(+)/K(+) ratio and further slight decrease in Na(+),K(+)-ATPase activity. These results indicate that opacity is partially reversed in rat lenses with a slight opacity induced by methylprednisolone hemisuccinate when the steroid treatment is withdrawn, and suggest that recovery of impaired lens membrane function could be involved in this in vitro partial opacity reversal.