Urinary levels of nitric oxide metabolites in normal pregnancy and preeclampsia.

Abstract

The purpose of this study is to clarify the physiological role of nitric oxide (NO) in normal pregnancy and preeclampsia. Thirty normotensive women (1st trimester, n = 7; 2nd trimester, n = 6; 3rd trimester, n = 10; puerperal period, n = 7) and 19 patients with preeclampsia (3rd trimester, n = 9; puerperal period, n = 10) were studied. Urinary and blood samples were obtained from each participant who was designed to be under the same condition. Urinary NOx (nitrate/nitrite) was measured with Greiss method after nitrate reduction. Urinary cyclic guanosine 3',5'-monophosphate (cGMP), creatinine clearance, serum triglyceride, uric acid, albumin and blood cell count were also determined. 1) Urinary NOx levels in 2nd and 3rd trimester of normal pregnancy tended to be higher than those in 1st trimester. There was also a tendency of decreased urinary NOx in puerperal period. Urinary NOx in antepartum preeclampsia was significantly lower than that of normal pregnancy in 3rd trimester. 2). Urinary cGMP was significantly higher in 2nd trimester of normal pregnancy than in 1st trimester. There was also a tendency of decreased urinary cGMP in puerperal period. In preeclampsia the values in 3rd trimester were significantly higher than those in puerperium. 3) A significant positive correlation was observed between urinary NOx and cGMP only in 3rd trimester of normal gestation. 4) In normal pregnancy of 3rd trimester, significant negative correlations were observed between urinary NOx and either of mean blood pressure or serum triglyceride. In preeclampsia of antepartum, urinary excretion of NOx was significantly correlated positively with creatinine clearance and negatively with mean blood pressure or serum uric acid. Urinary excretion of NOx in both of normal pregnant and preeclamptic women in 3rd trimester was significantly correlated with serum triglyceride. It is suggested that NO may modulate the cardiovascular changes during pregnancy and impaired production of the molecule may play a significant role in the pathophysiology of preeclampsia.