The nitric oxide synthase activity and expression in human placenta from preeclamptic pregnancies

Won, Hye Sung; Lee, Pil Ryang; Lee, In Sik; Kim, Ahm; Nam, Joo Hyun; Mok, Jung Eun

Abstract

OBJECTIVE
The changes of the production of nitric oxide in preeclampsia are still controversial. To determine the changes of nitric oxide production in preeclamptic pregnancies, NOS activity and eNOS and iNOS expression in preeclamptic placentae were compared with those in normal placentae, and to determine the changes of nitirc oxide production according to the sites of placenta, NOS activity and eNOS expression in preeclamptic placentae were also compared with those in normal placentae.
METHODS
Human placentae were obtained from 15 normal and 15 preeclamptic pregnant women at the time of cesarean section. NOS activity was assessed by measuring the conversion of [3H]-arginine into [3H]-citrulline. The eNOS and iNOS expression were assessed by using western blot analysis. Data were analyzed by Student t-test and paired t-test where appropriate.
RESULTS
The NOS activity(judged by measurement of [3H]-citrulline production) was significantly increased in preeclamptic placentae compared to normal(P<0.05). In normal and preeclamptic pregnant placentae, the NOS activity in main stem villi was increased compared to that in terminal villi. However, the difference of NOS activity between main stem villi and terminal villi was not significant(P>0.05). Quantification of the autoradiographic images demonstrated that the integrated optical density of the immunoreactive bands of eNOS were significantly lower in preeclamptic placentae compared to normal(p<0.05). Conversely, the integrated optical densities of the bands of iNOS were significantly higher in preeclamptic placentae compared to normal(p<0.05).
CONCLUSIONS
Although the eNOS expression in preeclamptic placentae was lower than that in normal placentae, the NOS activity was significantly higher in preeclamptic placentae than that in normal in this study. These are result from increased production of iNOS in the compensatory mechanisms for the decreased nitric oxide production in pre-eclamptic placentae.