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Regular Article |
a Perinatal Research Laboratories, Departments of Obstetrics/Gynecology and
b Animal Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53715
ABSTRACT
During the third trimester, fetoplacental and uterine blood flows increase dramatically to meet the high metabolic demands of the growing fetus. We hypothesized that the expression of endothelial nitric oxide synthase (eNOS) in fetoplacental artery endothelium and the concentrations of nitric oxide (NO) and cyclic GMP (cGMP) in amniotic fluid (AF) are increased during the third trimester of ovine gestation. Placental arteries and AF were collected from ewes at 110, 120, 130, and 142 days of gestation (n = 24; mean ± SEM term = 145 ± 3 days). Expression of eNOS protein was measured in intact and denuded placental arteries and in endothelium-derived protein by Western analysis and confirmed by immunohistochemistry. Concentrations of NO (nitrates plus nitrites) and cGMP were determined in AF. Placental artery eNOS protein expression was localized to the endothelium, where it was markedly greater than in vascular smooth muscle. Placental artery endothelium-derived eNOS expression and AF cGMP concentrations were similar at 110 and 120 days of gestation; however, both peaked at 130 days at levels two- to threefold above baseline (P < 0.05) before returning to baseline at 142 days of pregnancy. The AF NO (nitrates plus nitrites) levels, however, increased progressively between 120 days of gestation and term (P < 0.05). We concluded that endothelium-derived placental artery eNOS levels, AF NO (nitrates plus nitrites), and AF cGMP were markedly increased during the third trimester, thus supporting a role for NO-mediated elevations in cGMP in the control of fetoplacental blood flow.
First decision: 27 September 2000.
1 This investigation was supported by National Institutes of Health grants HL49210, HL57653, HD33255, HL56702, and HD38843 and American Heart Association-Wisconsin Affiliate 95GS-74. Dr. Sheppard was a fellow in Maternal Fetal Medicine.
2 Correspondence: Ronald R. Magness, Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Perinatal Research Laboratories, 7E Meriter Hospital/Park, 202 S. Park St., Madison, WI 53715. FAX: 608 257 1304; rmagness{at}facstaff.wisc.edu
3 Current address: Scott and White Ob/Gyn Clinic, Temple, TX 76508.
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