IMMUNOHISTOCHEMISTRY OF CARBONIC-ANHYDRASE IN HUMAN PLACENTA AND FETAL MEMBRANES

The localization of human carbonic anhydrase (CA) isoenzymes HCA I, HC A II, and rat CA II have been studied in human umbilical cord, chorion laeve including amnion and placenta from first and second trimester a nd also from term pregnancies. Detection techniques of immunofluoresce nce and immunoperoxidase were used in cryostat and paraffin sections. Both isoenzymes were found in the villous syncytiotrophoblast througho ut pregnancy. HCA I staining patterns in the villous endothelium were highly variable whereas increasing immunoreactivity levels of endothel ial HCA II were detected as pregnancy advances. The extravillous cytot rophoblast showed generally weaker levels of immunoreactivity. In amni onic epithelium of membranes, chorionic plate and umbilical cord, high er activities for HCA I, HCA II and rat CA II were found than in all o ther localizations. Our findings emphasize the importance of enzyme me diated bicarbonate/CO2 removal from the fete-placental unit as opposed to simple bicarbonate diffusion or carrier mediated transport. As eff ective transfer routes should be considered not only umbilical cord - placental villi - intervillous space, but also fetal kidney - amnionic fluid - amnion - uterine vessels.