Globulization alters light transmission through lens fiber cells without protein aggregation or cross-linking

Purpose. To investigate the mechanism by which globulization alters light transmission through single fiber cells isolated from rat lens cortex. Methods. Fiber cells were isolated from rat lenses by trypsin digestion and suspended in isomolar buffered sucrose solution (Exp. Eye Res. 61, 303, 1995). The fibers were superfused with Ringer's solution containing 1 mM calcium to elicit globulization. Transmitted light through the fiber cells and globules illuminated by a standard light source, was quantified by digital image analysis. Aggregation of crystallins in the cytoplasm was determined by electron microscopy. Protein cross-linking was measured by gel electrophoresis. Results. Fiber cells superfused with Ringer's solution containing 1 mM calcium completely globulized in 30 ± 3 min. Image analysis of the fiber cells showed an initial decrease in the intensity of the transmitted light through the fiber, accompanied by cell-swelling, Blebbing and disintegration of the fiber cells led to a marked increase in the transmitted light, possibly due to increased light reflection through the spherical globules. The electrophoretic mobility of the crystallins was not altered by globulization. In electron micrographs, the cytoplasm of the fibers and globules appeared homogenous indicating no significant protein aggregation. Conclusions. Changes in the shape of the fiber cells during globulization causes significant alterations in the light transmission properties without aggregation or cross linking of proteins. Similar gloulization may contribute to the light scattering centers in supranuclear cataracts.