title: Histochemical demonstration of exopeptidases in the rat visceral yolk-sac epithelium.
abstract: The localization of exopeptidase activities was demonstrated histochemically (by simultaneous azo coupling) on the visceral endoderm of whole unfixed yolk sacs of rats (12.5-18.5 days of gestation). For comparison, the topochemistry of exopeptidases was studied by conventional section histochemistry of frozen yolk sacs. The study of unfixed visceral yolk-sac epithelium showed that different artificial peptidase substrates (Ala-, Met-, Phe-, Leu-, alpha-Asp-, alpha-Glu-, gamma-Glu, Tyr-, Val-, Ser-, Arg- and Gly-Pro-MNA) are hydrolysed in the apical-cell membranes (membrane-bound peptidases) and, in a number of cells, within the cytoplasmic matrix. Section histochemistry showed that peptidase activities were almost only directed against gamma-Glu- and Gly-Pro-MNA at the cell apices. It is concluded that most of the exopeptidase activities in the apical cell membrane of the visceral yolk-sac epithelium are only demonstrable in unfixed yolk sacs. These activities are of great importance for the supplying of the embryo with amino acids.
authors.forename: P
authors.initials: P
authors.lastname: Kugler
authors.forename: A
authors.initials: A
authors.lastname: Huber
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives / Q000378:metabolism; D000578:Amidines; D000626:Aminopeptidases / Q000378:metabolism; D000818:Animals; D004151:Dipeptides / Q000378:metabolism; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism*; D004848:Epithelium / Q000201:enzymology; D005260:Female; D005973:Glutamine / Q000031:analogs & derivatives / Q000378:metabolism; D006651:Histocytochemistry; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity; D015017:Yolk Sac / Q000201:enzymology*; D005723:gamma-Glutamyltransferase / Q000378:metabolism
chemical_list: D000578:Amidines; D004151:Dipeptides; C031455:diamidino compound 253-50; D005973:Glutamine; C028104:alanine-beta-naphthylamide; C023861:gamma-glutamyl-2-naphthylamide; C039234:glycyl-proline-1-naphthylamide; D005723:gamma-Glutamyltransferase; D010450:Endopeptidases; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D000409:Alanine