title: Ultrastructural localization of aminopeptidase A/angiotensinase and placental leucine aminopeptidase/oxytocinase in chorionic villi of human placenta.
abstract: OBJECTIVE
  Membrane-bound aminopeptidases in human placenta are thought to be involved in maintaining homeostasis during pregnancy by metabolizing bioactive peptides such as oxytocin and angiotensin at the interface between the fetus and mother. Because determining the precise localization of these enzymes is required to support this notion, we investigated the ultrastructural localization of two principal enzymes, aminopeptidase A (APA; EC 3.4.11.7)/angiotensinase and placental leucine aminopeptidase (P-LAP; EC 3.4.11.3)/oxytocinase in human first trimester and full-term placenta.
  
  
  METHODS
  Immunohistochemical analysis using anti-P-LAP and anti-APA antibodies was performed on ultrathin frozen sections of fixed human placental villi.
  
  
  RESULTS
  Transmission immunoelectron microscopy revealed that both enzymes were expressed on the surface of apical microvilli of syncytiotrophoblast cells and, to a lesser extent, on the basal infoldings. The location of the two enzymes did not vary between the first trimester and full-term placenta sections, while the staining intensities were slightly enhanced in full-term villi.
  
  
  CONCLUSIONS
  Our observation that P-LAP and APA are present on the microvilli, which is a site of interaction between the mother and fetus, suggests possible involvement of these enzymes in cleaving peptide hormones from the fetus and mother in order to regulate bioactivity.
authors.affiliation: Department of Obstetrics and Gynecology, Graduate School of Medicine, Nagoya University, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Ito
authors.forename: Seiji
authors.initials: S
authors.lastname: Nomura
authors.forename: Akira
authors.initials: A
authors.lastname: Iwase
authors.forename: Tomomi
authors.initials: T
authors.lastname: Ito
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ino
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Nagasaka
authors.forename: Masafumi
authors.initials: M
authors.lastname: Tsujimoto
authors.forename: Miya
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Shigehiko
authors.initials: S
authors.lastname: Mizutani
mesh_terms: D000328:Adult; D000626:Aminopeptidases / Q000378:metabolism*; D002824:Chorionic Villi / Q000201:enzymology* / Q000648:ultrastructure; D010122:Cystinyl Aminopeptidase / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism*; D005260:Female; D043384:Glutamyl Aminopeptidase; D006801:Humans; D007124:Immunoenzyme Techniques; D008871:Microvilli / Q000378:metabolism / Q000648:ultrastructure; D011247:Pregnancy
chemical_list: C076819:angiotensinase; D010450:Endopeptidases; D000626:Aminopeptidases; D010122:Cystinyl Aminopeptidase; C105964:leucyl-cystinyl aminopeptidase; D043384:Glutamyl Aminopeptidase