FOR RELEASE:6 p.m. ET, TuesdayOctober 24, 2000
CONTACT:Maggie Francis (214) 706-1397
Carole Bullock (214) 706-1279[email protected]
Abstracts P40 & P18
American Heart Association meeting report: Hormones produced during pregnancy give insight into high blood pressure
WASHINGTON, Oct. 24 -- Pregnant women who develop preeclampsia, a condition characterized by high blood pressure, have abnormally low levels of a hormone that helps blood vessels relax, scientists report at the 54th Annual Fall Conference of the American Heart Association's Council for High Blood Pressure Research.
Two separate research teams report that in a normal pregnancy, elevated levels of the hormone angiotensin-(1-7) [Ang-(1-7)] may help maintain healthy blood pressure by dilating, or relaxing, blood vessels. In women with preeclampsia, Ang-(1-7) levels drop, possibly causing constriction of arteries and elevated blood pressure as blood is forced through narrowed vessels.
The scientists hope that further research based on their work will result in the development of better tests, treatments and prevention for preeclampsia.
Preeclampsia complicates about 5 percent of all pregnancies in the United States and is one of the leading causes of pre-term birth, says David Merrill, M.D., Ph.D., a co-author of one of the studies and associate professor in the department of obstetrics and gynecology at Wake Forest University School of Medicine, Winston-Salem, N.C. Women who develop preeclampsia are usually hospitalized so the condition can be stabilized, then labor is induced or a caesarean section is performed since delivery is the only known cure for preeclampsia.
Because preeclampsia patients are so closely monitored, women rarely die of the condition -- but they are at increased risk for stroke and liver complications, Merrill says. Infants born to preeclamptic women tend to be underweight and may require intensive care.
The study involved 15 preeclampsia patients and 15 healthy pregnant women. Fifteen non-pregnant women were also included for comparison. Using blood samples, the team observed the activity of four substances involved in the maintenance of blood pressure: Ang-(1-7), angiotensin I, angiotensin II and renin. Production of all of these is increased during pregnancy, but the preeclampsia patients had lower levels of all the substances compared to those with normal pregnancies.
"It's the first time Ang-(1-7) has been measured in pregnant women," says K. Bridget Brosnihan, Ph.D., primary author of the study and professor in the hypertension and vascular disease center at Wake Forest. "Indeed, we found Ang-(1-7) levels were reduced in preeclampsia, suggesting that a lack of it could be related to blood vessel constriction."
Merrill and Brosnihan are planning studies to observe Ang-(1-7) activity before the onset of preeclampsia to determine if women can be screened for the condition. Merrill says he also plans studies to determine if a genetic pattern is responsible for the imbalance.
A separate study in Chile evaluated average urinary levels of Ang-(1-7) in healthy women: nine who were in the ovulation phase of their menstrual cycle and 10 women with a normal pregnancy. Levels of Ang-(1-7) were higher among the pregnant women compared to the others, and these levels increased throughout the pregnancy.
"The rise in Ang-(1-7) levels started from 12 to 13 weeks of pregnancy to achieve a maximal value at 33 to 35 weeks. The pregnant women attained levels 13-fold higher than those observed among women during the ovulation phase of their menstrual cycle," says Gloria Valdes, M.D., of Pontificia Universidad Catolica School of Medicine in Santiago, Chile.
Ang-(1-7) is one of several hormones that help maintain blood pressure during pregnancy, Valdes says, but it appears that each is active during a different phase of pregnancy -- as if they form a "relay system." It also appears that some of the same substances play a role in the development and function of the placenta, through which blood flows to the fetus. Thus, the development of preeclampsia may be related to some impairment in the placenta's ability to conduct blood, Valdes suggests.
Valdes says it will be important to find out whether administering Ang-(1-7) to women with preeclampsia can halt the development of the condition.
Co-authors with Valdes were Brosnihan, Alfredo M. Germain, M.D.; Cecilia Berrios, M.D.; Jenny Corthorn, M.D.; and Carlos M. Ferrario, M.D.Co-author with Merrill and Brosnihan was Michael Karoly, M.D.###
NR00-1202 (HBP2000-Merrill)
Media advisory: Dr. Brosnihan can be reached by phone at (336) 716-2795 or by e-mail at [email protected]; Dr. Merrill can be reached by phone at (336) 716-4615 or by e-mail at [email protected]; Dr. Valdes can be reached by phone at 56-22-18-6349 by fax at 56-26-39-7377 or by e-mail at [email protected]. (Please do not publish telephone numbers or e-mail addresses.)
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