Morphological and Cell Volume Changes in the Rat Lens During the Formation of Radiation Cataracts.

摘要

Preliminary studies showed that x-irradiation caused an increase in the volume of postnatal rat lens epithelial cells. This increase in epithelial cell volume was followed by swelling of the underlying lens fibers, suggesting a correlation between impaired epithelial cell volume regulation and subsequent fiber cell swelling. To test this hypothesis, 4-week-old Sprague Dawley rats were injected with [3H]-thymidine and, 24 hrs. later, their eyes irradiated with either 4 or 12 Gy (1 Gy = 100 rads). Lenses were examined with a slit lamp and cataracts graded on a scale of 1+ to 4+. Animals were killed 24 hrs., 3, 5, 15, and 30 wks. after exposure. Lenses were serially sectioned at 0.75 urn and average cell volumes of specific lens regions determined. The surface morphology of fiber cells from these lenses and their attachment at the posterior suture were examined by scanning electron microscopy. Lenses were also labelled with [35 S] methionine and the incorporation of radioactivity into the crystallin, cytoskeletal and membrane protein fractions was examined by SDS-PAGE. Rats exposed to 4 or 12 Gy developed 0.5-1.5+ or 2.5-3.0+ cataracts, respectively, 10 to 16 wks. after x-irradiation. Epithelial and equatorial cells of both groups did not significantly increase in volume during this period. Three wks. after irradiation with 12 Gy cortical fibers were disorganized and their volume was increased transiently. By 5 wks. cortical fibers returned toward control cell volumes, although their morphology remained altered. Cortical fiber volume in lenses irradiated with 4 Gy was not significantly different from control lenses throughout the period examined. Wet weight determinations showed that the localized swelling of the cortical fibers did not result in an increase in the wet weight of the entire lens. Autoradiography results indicated that affected fibers had been epithelial cells at the time of irradiation.