Immunoelectron microscopic localization of cathepsin D in lysosomes of rat nerve cells.

Immunoelectron microscopic localization of cathepsin D in rat nerve cells was investigated using protein A-gold technique. Brain and spinal cord were fixed by perfusion with 4% paraformaldehyde and 1% glutaraldehyde in 0.05 M cacodylate buffer. Vibratome sections of the cerebellum and spinal cord were embedded in Epon 812 or Lowicryl K4M. The postembedding immunocytochemical procedures with protein A-gold were applied to ultrathin sections. Gold particles representing the antigen sites of cathepsin D were localized in lysosomes of Purkinje cells and of presumed motorneurons in the anterior horn. A few gold particles were in Golgi stacks of these cells. The results indicate that the main subcellular domain for cathepsin D in rat nerve cells is lysosome.