Placental nitric oxide synthase (NOS) activity and nitric oxide (NO) production in normal pregnancy, pre-eclampsia and eclampsia.

OBJECTIVES: To measure nitric oxide synthase (NOS) activity and total nitrites levels (as an index of nitric oxide 'NO' production) in placental villous homogenate of normal, pre-eclamptic and eclamptic pregnant women. DESIGN: Two groups were studied cross-sectionally: late pregnant women with pre-eclampsia and eclampsia (n=31) and normal pregnant women (all late) as controls (n=32). Two tissue blocks of whole placenta, each 1 x 1 x 1 cm, were collected at delivery and assayed for NOS activity and total nitrite levels. SETTING: Department of Obstetrics and Gynecology, Assiut University Hospitals, Egypt. METHODS: Placental tissues were homogenized and villous homogenates were assayed for NO production by Griess reaction which measures the combined oxidation products for NO (nitrites and nitrates) after reduction with nitrate reductase. NOS activity was determined by measuring NO synthesis by tissue extracts spectrophotometrically using the oxidation of oxyhemoglobin to methemoglobin by NO. RESULTS: Placental villous homogenates of pregnancies complicated by pre-eclampsia and eclampsia had significantly higher NOS activity and total nitrites levels compared with those of normal pregnancy [for NOS (P<0.0001) and for total nitrites (P<0.001)]. CONCLUSIONS: (1) Placental NOS activity and NO production are significantly increased in pre-eclampsia and eclampsia than those of normal pregnancy; this increase was directly related to the severity of this disorder. (2) Such increase possibly represents a physiologic adaptive response to overcome the increased placental vascular resistance and to minimize platelet and leukocyte adhesion to the surface of placental villi or within the intervillous spaces.

Maternal and fetal serum nitric oxide (NO) concentrations in normal pregnancy, pre-eclampsia and eclampsia.

OBJECTIVES: To measure the maternal and fetal serum concentrations of total nitrites and nitrates (as an index of nitric oxide production) in normal pregnancy, pre-eclampsia and eclampsia. DESIGN: Three groups of women were studied cross-sectionally: late pregnant women with pre-eclampsia and eclampsia (n=31); normal late pregnant women (n=32); and age-matched healthy non-pregnant women (n=21). Venous blood samples were collected from all women and both maternal and umbilical venous samples were collected from pregnant women. METHODS: Blood samples were assayed for nitric oxide (NO) production by Greiss reaction which measures the combined oxidation products of NO (total nitrites and nitrates). RESULTS: There was a significant increase in serum total nitrites and nitrates concentrations in normal pregnant women than in the serum of age-matched normal non-pregnant women (P<0.0001). Significantly higher total nitrites and nitrates levels were found in the maternal sera of the pre-eclamptic and eclamptic women compared with those of normal pregnant women (P<0.0001). Also, fetal blood levels of total nitrites and nitrates were significantly increased in pre-eclampsia and eclampsia compared with those of normal pregnancy (P<0.0001). CONCLUSIONS: (1) Serum nitric oxide (NO) production is increased in normal pregnancy than in the normal non-pregnancy. (2) Maternal and fetal serum NO levels are increased significantly in pre-eclampsia and eclampsia, which possibly represents a compensatory/protective mechanism to maintain blood flow and limit platelets aggregation in the fetal-maternal circulations. (3) The increase in NO production is directly related to the severity of pre-eclampsia; this would be of diagnostic significance for the prediction of the severity of this syndrome.