ScienceDaily (June 14, 2001) — DALLAS, June 8 – Researchers have identified reduced blood levels of available nitric oxide as a cause of preeclampsia – a life-threatening condition that causes, among other things, high blood pressure during pregnancy, according to a report in the June 8 issue of Circulation Research: Journal of the American Heart Association.

Preeclampsia is a major cause of severe complications and death for both mother and newborn. Nitric oxide (NO) is produced by the blood vessels and helps the vessels relax, which eases blood pressure.

Researchers took blood samples from 21 pregnant women with preeclampsia and 21 women with normal pregnancies. Those with preeclampsia had elevated blood levels of S-nitrosothiols, substances that act as a major reservoir of releasable NO, which means NO was not being released. The levels of S-nitrosothiols were 294 picomole per milligram (pmol/mg) of protein in women with preeclampsia vs.186 pmol/mg in those with healthy pregnancies. A substance called S-nitrosoalbumin, a type of S-nitrosothiol formed from albumin (the most abundant protein in blood plasma), was the major contributor to the elevated levels of S-nitrosothiols in preeclampsia. Its levels were significantly higher in preeclamptic than in normal pregnant or nonpregnant women (256, 137, and 94 pmol/mg protein, respectively).

The increases in these substances in preeclamptic women may reflect insufficient release of NO, an important physiological regulator of blood pressure. Further studies are needed to test whether antioxidant vitamins, particularly vitamin C, which seems to reduce the incidence of preeclampsia, might also enhance the release of NO from S-nitrosothiols.

This research was funded in part from the National Institutes of Health.

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