Expression of nitric oxide synthase in normal and preeclamptic placental tissue and effects of glyceryl trinitrate and shear stress on placental blood flow

BACKGROUND: To study the expression of constitutively expressed nitric oxide synthase (cNOS) as well as the effects of glyceryl trinitrate (GTN) and shear stress on normal and preeclamptic placental tissue. METHODS: The expression of cNOS was studied using NADPH diaphorase activity reaction in seven normal and four preeclamptic placentas. The effect of GTN (n = 5) and shear stress induced by increasing the flow rate in the perfusion system (n = 5) was studied using an in vitro placental perfusion method. RESULTS: No difference in the distribution of cNOS in placental tissue was found between preeclamptic and normal pregnancies. Shear stress did not affect the production of nitric oxide metabolites. GTN was able to dilate placental vasculature. CONCLUSIONS: cNOS derived from syncytiotrophoblasts may not contribute to the development of preeclampsia. Placental vasculature responds to nitric oxide by vasodilation.