IMMUNOHISTOCHEMICAL STUDY OF CALPAIN-MEDIATED ALPHA-CRYSTALLIN PROTEOLYSIS IN THE UPL RAT HEREDITARY CATARACT

The UPL (Upjohn Pharmaceutical Limited) rat is a dominant hereditary c ataract model that develops early-onset cataracts (E-type) in rats hom ozygous for the trait, and late-onset cataracts (L-type) in heterozygo us rats. Using antibodies specific to the calpain-proteolyzed forms of alpha-crystallin, we determined their immunohistochemical localizatio n of the L- and E-rat lenses. Immunoreactivity indicating the proteoly zed forms was detected and found restricted to degenerated lens fibers of the mature stage of the L-rat cataract. Lenses from E-rats, which have abnormally elongated lens fibers during the fetal period, had pro teolyzed alpha-crystallin forms at 1 week of age. The results of this present study indicate that calpain-mediated proteolysis of alpha-crys tallin occurred in the UPL rat lenses during cataract formation and th at calpain may be an important factor in the development of complete l ens opacification. (C) 1997 Japanese Ophthalmological Society.