Lysosomal cysteine proteinases in rat epididymis.

To examine the precise localization of lysosomal cysteine proteinases, cathepsins B, H, and L in rat epididymal epithelial cells, immunohistochemistry and enzyme assay were applied to the epididymal tissue. Granular immunodeposits for cathepsins B and H were detected in epididymal epithelial cells, whereas faint or no immunoreactivity for cathepsin L was found. Moreover, immunoreactivity for cathepsin B appeared mainly in principal cells and was more intense in the head of the epididymis than in the tail, whereas that for cathepsin H appeared in both principal and clear cells and was more intense in the tail than the head. By enzyme assay, activities of cathepsins B and H showed a similar distribution to that of the immunoreactivity. The cathepsin L-specific activity was distributed evenly in each part of the epididymis and was also detected in epididymal fluids obtained from the body and tail parts. By immunoblotting, proforms of cathepsins B, H, and L were present in the seminal fluid. The results suggest that cathepsins B and H are involved in the intracellular degradation system of epididymal epithelial cells, and proforms of cathepsins B, H, and L may be secreted into the epididymal duct lumen.