Oxytocin regulates oxytocinase of human vascular endothelial cells

Oxytocinase (OTase) degrades several small peptides such as oxytocin (OT), and plays important roles in fetal development and maintenance of homeostasis during pregnancy The physiological effects of OTase are mediated via its receptor (OTR). Although the interactions between OT and OTR have been studied extensively, the relationship between OT OTR and OTase has never been clarified. It is already known that human umbilical vein endothelial cells (HUVECs) express mRNA of OTR. In the present study. we have focused on these issues. RT-PCR analysis on HUVEC showed the existence of mRNA of OTase. Our present data clarified that OT stimulated the cell-surface activities of OTase via OTR, In addition, OT stimulation on HUVEC was considered to involve translocation of OTase from the cytosol to the cell surface, In terms of this phenomenon, the cellular signal transduction pathways linked to the OTR were undoubtedly responsible. The protein kinase C (PKC stimulator significantly stimulated the cell-surface activities of OTase as well as its inhibitor which inhibited them. In summary, these Findings clearly show evidence that OT directly triggers OTase translocation in HUVEC via the PKC-dependent pathway coupled to OTR. This is the first report on the pathway in the metabolism of OT at the cellular level.