Immunohistochemical localization of placental leucine aminopeptidase/oxytocinase in normal human placental, fetal and adult tissues

Abstract

While oxytocinase is known to exist in pregnancy serum and placenta, thepresent study describes the expression of the mRNA for this enzyme in a widevariety of other human tissues. Northern blot analysis was used to detect themRNA, with a probe derived from a cDNA for oxytocinase/placental leucineaminopeptidase (P-LAP). Both the distribution and localization ofimmunoreactive oxytocinase/P-LAP protein have been determinedimmunohistochemically by use of an anti-P-LAP antibody in normal placental,fetal and adult tissues. In placental tissues, only syncytiotrophoblasts werestained positively. In both fetal and adult tissues, positive staining wasobtained in vascular endothelial cells, gastrointestinal mucosal cells,epithelial cells of hepato-biliary, pancreato-biliary, bronchial-alveolar andrenal tubular systems as well as islet cells of pancreas and neurons in thecentral nervous systems. Sweat-gland cells, seminal vesicles and prostategland in the adult, as well as adipocytes and skeletal muscle cells in thefetus were also stained. The widespread distribution of P-LAP suggests itsinvolvement in a variety of physiological events not restricted to theregulation of the amounts of bioactive peptides such as arginine vasopressin(AVP) and oxytocin (OT) in pregnancy. The presence of P-LAP insyncytiotrophoblasts supports the idea that P-LAP in pregnancy serum isderived from the placenta.