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(Circulation Research. 2000;87:344.)
© 2000 American Heart Association, Inc.

Editorial

Vascular Control During Pregnancy

Extending Experimental Findings to Humans

Virginia M. Miller

From the Departments of Surgery and Physiology and Biophysics, Mayo Clinic, Rochester, Minn.

Correspondence to Virginia M. Miller, PhD, Professor of Surgery and Physiology, Departments of Surgery and Physiology and Biophysics, Mayo Clinic, 200 First St SW, Rochester, MN 55905. E-mail miller.virginia@mayo.edu

Key Words: hormones • endothelium • nitric oxide synthase • vascular remodeling • uterine artery

	Introduction

 
It has been known for more than 50 years that estrogen increases blood flow to uterine tissue.^{1 2} Indeed, perhaps one of the most dramatic effects of hormones on modulation of a circulatory system is change in uterine blood flow during pregnancy. Much has been learned about mechanisms contributing to these changes in blood flow from studies performed in experimental animals. For example, observations of nonneuronal vasodilatory effects of acetylcholine in uterine arteries and the time course for modulation of this response by pregnancy and estrogen preceded discovery of endothelium-derived relaxing factors.^{3 4 5} These original observations provided some of the first hints as to both an immediate, nongenomic and longer-term modulation of vascular responses by sex steroid hormones. Subsequently, nitric oxide was identified as one of the endothelium-derived factors modulated by estrogen in systemic blood vessels as well as blood vessels of the reproductive system.^{6 7 8 9 10 11} In this issue of Circulation Research, Nelson et al¹² extend these observations by investigating expression of isoforms of nitric oxide synthase (NOS) in uterine arteries from women after normal pregnancies compared with those from multipara, nonpregnant women. Results of this study confirm observations in experimental animals: NOS expression increases in uterine arteries during pregnancy and NOS immunostaining increases in uterine arteries during the follicular compared with luteal phase of the menstrual cycle in nonpregnant women.

In the era of translational or bench-to-bedside research, studies involving human tissue are necessary to validate observations in experimental animals, because each type of study carries certain limitations. Results from animal . . . [Full Text of this Article]