Article Abstract:
Uterine arteries may respond more sensitively to increases in blood pressure than abdominal arteries. Researchers obtained uterine and abdominal arteries from term pregnant women and compared the contraction response of uterine muscle arteries to that of abdominal arteries. Nitric oxide inhibitors did not increase the contraction tone of arteries, suggesting that nitric oxide does not contribute to the contraction response. A drug-induced relaxation response was more pronounced in uterine than abdominal arteries. Uterine arteries may have different contraction and relaxation properties than other arteries.
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Article Abstract:
The pregnant uterus may activate a constricting substance in the upper uterus and a relaxing substance in the lower uterus during active labor. Researchers biopsied the upper uterus, lower uterus, and cervix in 16 pregnant and eight nonpregnant women to determine endothelin receptor type A and B (ET-A, ET-B) gene expression in each site. Greater expression of ET-A, which is known to stimulate smooth muscle contractions, was found in the upper uterus than in the lower uterus and cervix. The ET-B receptor, which relaxes muscle, was expressed more in the lower uterus.
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Article Abstract:
The study evaluates the role of the ETA receptor and nitric oxide (NO) in the regulation of uteroplacental and renal blood flow in pregnant rats. There is an important role for endogenous ET in the regulation of the uteroplacental blood flow in the rat.
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