This Article Full Text Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Pascoal, I. F. Articles by Umans, J. G. Search for Related Content PubMed PubMed Citation Articles by Pascoal, I. F. Articles by Umans, J. G.

(Hypertension. 1996;28:183-187.)
© 1996 American Heart Association, Inc.

Articles

Effect of Pregnancy on Mechanisms of Relaxation in Human Omental Microvessels

Istenio F. Pascoal; Jason G. Umans

the Departments of Medicine and of Obstetrics and Gynecology, and the Committee on Clinical Pharmacology, Division of the Biological Sciences, University of Chicago (Ill). E-mail jumans@medicine.bsd.uchicago.edu.

We assessed mechanisms of acetylcholine- and bradykinin-induced relaxations in human omental resistance vessels. Ring segments (approximately 200 µm normalized ID) were dissected from omental biopsies obtained from women at laparotomy (nonpregnant) or at cesarean delivery (pregnant) and were studied under isometric conditions in a Mulvany-Halpern myograph. All arginine vasopressin-preconstricted vessels relaxed in a strictly endothelium-dependent manner to acetylcholine and bradykinin; maximal relaxations were not decreased by either N^G-nitro-L-arginine or indomethacin. By contrast, bradykinin failed to relax vessels that had been preconstricted with potassium gluconate. In the combined presence of N^G-nitro-L-arginine and indomethacin, addition of charybdotoxin, a selective antagonist of some calcium-sensitive potassium channels, did not inhibit maximal bradykinin-induced relaxation. By contrast, addition of 10 mmol/L tetraethylammonium chloride abolished relaxation in vessels from nonpregnant women but not in vessels from gravidas. We conclude that bradykinin relaxes these human resistance arteries in an endothelium-dependent but predominantly nitric oxide- and prostanoid-independent manner; relaxation likely depends on the action of an endothelium-derived hyperpolarizing vasodilator. Furthermore, in striking contrast to mechanistic insights from animal studies, human pregnancy appears to augment a mechanism of endothelium-dependent relaxation in these vessels that is insensitive to the inhibitors noted above. Whether a similar novel vasodilator mechanism in vivo contributes to the physiological vasodilation that characterizes human gestation or whether failure of such a mechanism might lead to preeclampsia remains the subject of future study.

Key Words: endothelium • vasodilation • resistance vessels • potassium channels • nitric oxide

This article has been cited by other articles:

				I. C Villar, A. J Hobbs, and A. Ahluwalia Sex differences in vascular function: implication of endothelium-derived hyperpolarizing factor J. Endocrinol., June 1, 2008; 197(3): 447 - 462. [Abstract] [Full Text] [PDF]

				L. Luksha, H. Nisell, N. Luksha, M. Kublickas, K. Hultenby, and K. Kublickiene Endothelium-derived hyperpolarizing factor in preeclampsia: heterogeneous contribution, mechanisms, and morphological prerequisites Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2008; 294(2): R510 - R519. [Abstract] [Full Text] [PDF]

				J. C. Gillham, J. E. Myers, P. N. Baker, and M. J. Taggart Regulation of Endothelial-Dependent Relaxation in Human Systemic Arteries by SKCa and IKCa Channels Reproductive Sciences, January 1, 2007; 14(1): 43 - 50. [Abstract] [PDF]

				L. Luksha, H. Nisell, and K. Kublickiene The mechanism of EDHF-mediated responses in subcutaneous small arteries from healthy pregnant women Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2004; 286(6): R1102 - R1109. [Abstract] [Full Text] [PDF]

				P. Coats, F. Johnston, J. MacDonald, J. J. V. McMurray, and C. Hillier Endothelium-Derived Hyperpolarizing Factor : Identification and Mechanisms of Action in Human Subcutaneous Resistance Arteries Circulation, March 27, 2001; 103(12): 1702 - 1708. [Abstract] [Full Text] [PDF]

				C. D. Figueroa, A. Marchant, U. Novoa, U. Forstermann, K. Jarnagin, B. Scholkens, and W. Muller-Esterl Differential Distribution of Bradykinin B2 Receptors in the Rat and Human Cardiovascular System Hypertension, January 1, 2001; 37(1): 110 - 120. [Abstract] [Full Text] [PDF]

				A. P. Cockell and L. Poston Flow-Mediated Vasodilatation Is Enhanced in Normal Pregnancy but Reduced in Preeclampsia Hypertension, August 1, 1997; 30(2): 247 - 251. [Abstract] [Full Text]