|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1993 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1992 : ¥1,600,000 (Direct Cost : ¥1,600,000)
The localizations and enzymatic activities of cathepsins B, D, and L, the most typical lysosomal proteinases, were determined by immunohistochemistry, enzymatic assay and immunoprecipitation in the trigeminal ganglion (TG) of young (2-3 months) and aged (28-31 months) rats. In the young rat, granular immunoreactive products of these enzymes showed homogeneous distributions through the cytoplasm. In the aged rat, however, immunoreactive products of these enzymes were found to be localized at a focal cytoplasmic site of most TG neuron forming coarse aggregates. At the immunoelectron microscopic level, immunoreactive products of cathepsin B were detected in mainly secondary lysosomes and partially primary lysosomes and residual bodies, which were accumulated at a focal perinuclear site of TG neurons from aged rat. Enzymatic activities of cathepsins B and L in the TG of aged rat were significantly lower than those of young rat, whereas cathepsin D activity was unchanged with aging. Cathepsin E, a non-lysosonmal aspartic proteinase, was not detected in TG neurons by either immunohistochemistry or enzymatic assay. The present study atrongly suggests that the focal accumulation of cathepsins B, L and D and the reduced activities of cathepsins B and L in the TG neurons of aged rat are closely linked with the increased autophagocytosis and the genesis of residual bodies and/or lipofuscins which are the most ubiquitous age-related cytological alteration. Thus, these enzymes, especially cathepsins B and L, can be used as markers of rate of aging as well as for increased phagocytosis in the TG neuronal system.