Cellular and subcellular localization of nicotinamide adenine dinucleotide phosphate diaphorase activity.

Abstract

To determine the cellular and subcellular distribution of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) in the human placenta and thereby to shed light on the possible role of nitric oxide (NO) and NO synthase in this tissue. NADPH-d activity in 10 term placenta and in 10 first-trimester placentas was examined by enzyme histochemistry and by both light microscopy and electron microscopy. Light microscopy revealed that NADPH-d activity was marked in the syncytiotrophoblasts, moderate in the endothelium of cord vessels, and weak in the amniotic epithelia and chorionic trophoblasts. At the electron-microscopic level, NADPH-d activity was apparent as small patches distributed throughout the cytoplasm of the syncytiotrophoblasts. NO might be generated in the syncytiotrophoblast of the human placenta and might play a role in the regulation of placental hemodynamics or in the signaling between the syncytium and the villous mesenchyme.