title: An improved procedure for the histochemical demonstration of cathepsin D by the mercury-labeled pepstatin method.
abstract: The desirable fixation conditions for the histochemical demonstration of cathepsin D using mercury-labeled pepstatin as an enzyme inhibitor were examined biochemically and histochemically. Four well known fixatives, namely, glutaraldehyde (GA), paraformaldehyde (PFA), glutaraldehyde with paraformaldehyde (GA-PFA) and periodate-lysine-paraformaldehyde (PLP), were applied to the prefixation of tissues prior to the reaction of the labeled inhibitor to the enzyme-active site. The effects of fixatives on cathepsin D were biochemically examined using subcellular fractionated lysosomes. Cathepsin D from rat liver lysosomes was rapidly inactivated by the fixatives containing glutaraldehyde, i.e., GA and GA-PFA, whereas the activity of cathepsin D was sufficiently maintained after fixing the enzyme in the PFA or PLP preparations. Effects of the PLP fixative on lysosomal cathepsin D in liver tissues using the mercury-labeled pepstatin method were also studied histochemically. The best result for the visualization of lysosomal cathepsin D in liver tissues was obtained using the PLP fixative with the prefixation time of three hours or more.
mesh_terms: D000818:Animals; D002402:Cathepsin D / Q000032:analysis*; D002499:Centrifugation, Density Gradient; D006651:Histocytochemistry; D008099:Liver / Q000648:ultrastructure; D008247:Lysosomes / Q000032:analysis; D008628:Mercury; D008854:Microscopy, Electron; D009842:Oligopeptides / Q000032:analysis*; D010436:Pepstatins / Q000032:analysis*; D051381:Rats; D013194:Staining and Labeling / Q000379:methods
chemical_list: D009842:Oligopeptides; D010436:Pepstatins; C014195:Streptomyces pepsin inhibitor; D002402:Cathepsin D; D008628:Mercury; C031375:pepstatin