Proteinases in pathology. Usefulness of histochemical methods

Z Lojda

The usefulness of optimized and newly elaborated histochemical methods for proteinases is illustrated on two selected substances. DAP IV (Gly-Pro-MNA,FBB,pH 7.2) was discovered in 39% and DAP II (Lys-Ala-MNA,FBB,pH 5.5) in 60% of the lymphocytes of human peripheral blood (ly). The reaction product of such ly differs in quality and quantity. On the ultrastructural level, the reaction product of DAP IV (Gly-Pro-MNA,HNF) was found in cell membranes and lysosomes. Enzyme activity in other areas was probably suppressed during the preparation procedure. Although the number of ly revealed with Lys-Pro-MNA and Phe-Pro-MNA at pH 5.5 and with Lys-Pro-MNA at pH 7.2 is high, these substrates do not distinctly discriminate DAP IV and DAP II. DAP IV occurs exclusively in T lymphocytes. The number of DAP IV-positive ly was not decreased in patients with myelofibrosis, plasmacytoma, chronic granulocytic leukemia, or tricholeukemia. It was, however, greatly reduced in chronic lymphatic leukemia (CLL). In patients with malignant lymphomas other than CLL, ly presence is related to the stage of the disease. Decreased values indicate a more severe stage or a relapse. In the majority of patients with gastric cancer DAP IV-positive ly were decreased. They were normal or increased in patients with peptic ulcer. The assessment of the number of DAP IV-positive ly is a simple method that provides information regarding the condition of patients with malignant lymphomas and gastric carcinoma. Neutrophilic leukocytes and their precursors, and to a lesser extent monocytes, are revealed when N-acetyl-Met-I-naphthyl ester (Ac-Met-N) is used as substrate. Membrane-bound lysosomal and cytosol proteinases were investigated together with disaccharidases in jejunal biopsies of patients with malabsorption syndrome. Activities of all enzymes were affected in patients with celiac disease. According to their impairment enzymes could be arranged: Lactase(L). trehalase (T), brush border endopeptidase (BBEP), gamma-glutamyl transferase (GGT), DAP IV, enzyme(s) cleaving Ac-Mer-N, aminopeptidase A, cytosol peptidases and aminopeptidase M. In the propria, DAP IV is decreased or absent, while GGT and, particularly, DAP II are increased. After a gluten-free diet, activities are restored in a reverse order. BBEP and GGT are useful as auxiliary parameters in the assessment of the damage or differentiation degree of enterocytes. DAP IV is a sensitive indicator of the involvement of the propria.
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