Expression and Tissue Localization of Soluble Guanylyl Cyclase in the Human Placenta Using Novel Antibodies Directed against theα 2 Subunit

The cytoplasmic or soluble forms of guanylyl cyclase (sGC) are heme-containing heterodimeric enzymes that are regulated by nitric oxide (NO) and carbon monoxide (CO). These gaseous messenger molecules are produced in the human placenta and are potential regulators of vasodilation and trophoblast invasion. The α2-subunit of sGC has only recently been shown to naturally occur in placental extracts. In the present study, two novel antibodies directed against different epitopes of the α2 subunit, were generated. Western Blot analysis confirmed the presence of a 82 kDa protein, identical with α2 protein overexpressed in Sf9 cells. According to RNase protection analysis the alternatively splicedα 2i variant was absent from human placenta. Immunohistochemical analysis showed the presence of α2 protein in syncytiotrophoblast and villous and umbilical blood vessels, which are known sites of NO production. Strong expression was observed in the extravillous (intermediate) trophoblast, where the expression of CO-gene...