Placental Production of Nitric Oxide and Endothelin in Normal and Preeclamptic Pregnancies

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Abstract
Objective: To examine the production rates of nitric oxide (NO) and en-dothelin in normal and preeclamptic placentas. We hypothesized that if placental production of NO is decreased and/or that of endothelin is increased in preeclampsia, these compounds could contribute to the pathophysiology of placental vasoconstriction. Methods: Human placental tissues were obtained from women with normal pregnancies (n = 8) and women with preeclampsia (n = 6). Tissues (350 mg) were incubated in DMEM for 48 h. Results: Both normal and preeclamptic placentas produced NO and endothelin progressively during the 48 h of incubation. The concentrations after 48 h for nitrite were 29 ± 8 nmol/mg protein for normal placentas and 34 ±11 nmol/mg protein for preeclamptic placentas. For endothelin, the concentrations after 48 h were 20 ± 3 fmol/mg and 23 ± 3 fmol/mg, respectively. There were no statistically significant differences for either NO or endothelin between normal and preeclamptic placentas, P ± 0.5. Conclusion: Whole placental villi produce NO and endothelin, and so these compounds are probably involved in the normal regulation of placental blood flow. However, there are no differences in the production rates between normal and preeclamptic placentas. Our data do not support a role for NO and endothelin in the pathophysiology of preeclampsia.