title: Enzyme histochemical discrimination between tryptase and chymase in mast cells of human gut.
abstract: We tested four synthetic substances for their histochemical value to demonstrate the catalytic activities of chymase or tryptase in mast cells in sections of human gut. Both Suc-Ala-Ala-Phe-4 methoxy-2-naphthylamide (MNA) and N-acetyl-L-methionine-alpha-naphthyl ester (alpha-N-O-Met) reacted with chymase but not tryptase in mast cells. Conversely, D-Val-Leu-Arg-MNA and Z-Ala-Ala-Lys-MNA were hydrolyzed by mast cell tryptase but not chymase. These results were confirmed by use of two inhibitors of chymotrypsin-like activity, chymostatin and Z-Gly-Leu-Phe-chloromethyl ketone (CK) and two inhibitors of trypsin-like activity, Tos-Lys-CK and D-Val-Leu-Arg-CK. Excellent staining reactions were obtained on cryostat sections of unfixed or aldehyde-fixed tissues and on paraffin sections of Carnoy-fixed tissues. For chymase, however, Suc-Ala-Ala-Phe-MNA is preferred on cryostat sections because it is more specific. On paraffin sections alpha-N-O-Met is preferred because other cells are not then stained. For tryptase, Z-Ala-Ala-Lys-MNA was more selective and more specific and is the preferred general purpose substrate on cryostat sections of aldehyde-fixed tissues and for paraffin sections. D-Val-Leu-Arg-MNA is the preferred substrate for cryostat sections of unfixed tissue. Only a limited number of mast cells showed a reaction for chymase, and these occurred mainly in the submucosa. All mast cells, however, gave a reaction for tryptase, and we recommend the use of either substrate for this enzyme for routine detection of mast cells in human tissues. Double staining for the two main mast cell proteases is most conveniently undertaken on paraffin sections of Carnoy-fixed tissues using MNA substrates for tryptase and alpha-N-O-Met for chymase.
authors.affiliation: Department of Oral Pathology, Rayne Institute, King's College School of Medicine and Dentistry, London, United Kingdom.
authors.forename: I A
authors.initials: IA
authors.lastname: Osman
authors.forename: J R
authors.initials: JR
authors.lastname: Garrett
authors.forename: R E
authors.initials: RE
authors.lastname: Smith
mesh_terms: D015081:2-Naphthylamine / Q000031:analogs & derivatives / Q000378:metabolism; D053818:Chymases; D004064:Digestive System / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D006651:Histocytochemistry / Q000379:methods; D006801:Humans; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology*; D008715:Methionine / Q000031:analogs & derivatives / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D009842:Oligopeptides; C058801:benzyloxycarbonyl-alanyl-alanyl-lysyl-4-methoxy-2-naphthylamide; C020854:N-acetylmethionine alpha-naphthyl ester; C038043:valyl-leucyl-arginine-4-methoxy-2-naphthylamide; C058802:succinyl-alanyl-alanyl-phenylalanyl-4-methoxy-2-naphthylamide; D008715:Methionine; D015081:2-Naphthylamine; D010447:Peptide Hydrolases; C023073:tosylarginine methyl ester hydrolase; D012697:Serine Endopeptidases; D053818:Chymases