Expression and Localization of NO Synthase Isoenzymes (iNOS and eNOS) in Development of the Rabbit Placenta

Abstract

Nitric oxide synthase (NOS) is a key regulator of angiogenesis and embryogenesis in the mammalian reproductive process. Here, we attempted to clarify the expression and localization of inducible and endothelial NOS (iNOS and eNOS) in the developing rabbit placenta. Real-time RT-PCR analysis indicated that iNOS mRNA was significantly upregulated during pregnancy, and then significantly decreased after d18 (completion of the placentation period). The eNOS mRNA was also enhanced in the pregnant uteri and gradually decreased near the term of pregnancy. Western blot analysis also showed elevation of the iNOS and eNOS protein levels during the course of pregnancy. Immunohistochemical study revealed distinct localizations of iNOS along the radial arteries and eNOS at the spiral arteries and arterial sinuses in the developing placenta. This may reflect that iNOS and eNOS participate in pregnancy success through placentation-specific vascular formation and by supporting adequate blood circulation in the rabbit placenta.