The state of sulfhydryl groups in normal and cataractous human lens proteins. II. Cortical and nuclear regions

Abstract

The effects of aging and development of senile cataract on the distribution of lenticular protein and total sulfhydryl groups (SH + SS) in the water-soluble and insoluble fractions of the cortex and nucleus of the human lens have been examined. In normal lenses between 33 and 80 years of age, protein and total SH + SS levels of both regions remain fairly constant. With the possible exception of the cortex of the most advanced cataracts, values for these parameters in senile cataracts of various stages show no significant change from those for normal 63-year-old lenses. In normal lenses between 18 and 80 years of age amounts of water-insoluble proteins increase from 20 to 44% of the total cortical protein and from 20 to 55% of the total nuclear protein. In mature cataracts as much as 60% of the cortical and more than 90% of the nuclear proteins can be water-insoluble. Protein disulfides, not detectable in the normal 18-year-old cortex, accumulate by 63 years of age to a level of about 9% of the total cortical SH + SS and 17% of the total nuclear SH + SS groups. The percentages of total SH + SS represented by protein disulfides in either the soluble or insoluble cataractous proteins of Groups II through IV show large increases beyond those in the normal 63-year-old lens. Absolute amounts of soluble protein disulfides, however, remain within the range of normal values. Nonprotein disulfides, i.e. TCA-soluble sulfhydryl groups released by borohydride, are present at low levels in the normal aging lens. The nuclear insoluble fraction of most cataractous lenses is characterized by marked increases in these groups. Losses of non-protein sulfhydryl groups during aging and cataract development are confined largely, if not entirely, to the soluble fraction of the cortical region.