NITRIC-OXIDE SYNTHASE IN HUMAN PLACENTA

Nitric oxide synthase is demonstrated immunohistochemically in the cyt osol, on granules, and on syncytiotrophoblasts membranes. The enzyme i s also detected on placental villous stroma cells, and on endothelial cells. The histochemical staining method NADPH-diaphorase stains the s yncytiotrophoblasts intensely, and stroma cells more weakly. Membranes of syncytiotrophoblasts immobilized on nitrocellulose paper are also stained by NADPH-diaphorase, and by antisera to nitric oxide synthase. Oxidases of sex steroid synthesis do, however, influence placental tr ophoblasts and there are discrepancies in the staining pattern of endo thelial cells. Caution should therefore be exercised when using NADPH- diaphorase as a staining method for nitric oxide synthase in placenta.