Departments of Gynecopathology (A.-M.B., T.L.) and Pharmacology (M.K., J.K., H.S., S.B.), University clinic Eppendorf, 20246 Hamburg, Germany
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 2-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
2 subunit, were generated.
Western Blot analysis confirmed the presence of a 82 kDa protein,
identical with
2 protein overexpressed in Sf9 cells.
According to RNase protection analysis the alternatively spliced
2i variant was absent from human placenta.
Immunohistochemical analysis showed the presence of
2
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-generating hemeoxygenases has recently been documented. Localization
of
2 subunit expression suggests a role for sGC in
mediating the actions of both NO and CO. The novel antibodies
characterized in the present study will be powerful tools to further
elucidate the role of the NO/CO/cGMP signaling pathways in pathologic
states such as preeclampsia and intrauterine growth retardation.