AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 5 1056-R1062, Copyright © 1989 by American Physiological Society

ARTICLES

Vasomotor responses of the umbilical circulation in fetal sheep

S. L. Adamson, R. J. Morrow, S. B. Bull and B. L. Langille
Department of Obstetrics and Gynecology, University of Toronto, Ontario, Canada.

The effects of vasoactive agents on the distribution of vascular resistance within the umbilical circulation of fetal sheep in utero has been assessed under general anesthesia. Under control conditions, 37% of the arterial to venous pressure drop occurred across the umbilical arteries and their major tributaries, 8% occurred across umbilical veins, and the remaining 55% occurred across the cotyledons. Isoproterenol had no significant effect on these resistances. Norepinephrine and angiotensin II both dramatically increased placental vascular resistance, but the distribution of resistances was altered in different ways. Angiotensin caused a 13-fold increase in the umbilical arterial resistance, whereas there were no changes in cotyledon or venous resistances. Norepinephrine also had no effect on cotyledon vascular resistance but it constricted downstream vessels (6-fold increase). These results suggest that norepinephrine and angiotensin II regulate fetal placental blood flow and that they can independently control pressure in placental exchange vessels. As a consequence, these agents may play an important role in controlling fetal-maternal fluid transport.

This article has been cited by other articles:

				J. P. H. M. van den Wijngaard, B. E. Westerhof, M. G. Ross, and M. J. C. van Gemert A mathematical model of twin-twin transfusion syndrome with pulsatile arterial circulations Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2007; 292(4): R1519 - R1531. [Abstract] [Full Text] [PDF]

				G. D. Giraud, J. J. Faber, S. S. Jonker, L. Davis, and D. F. Anderson Effects of intravascular infusions of plasma on placental and systemic blood flow in fetal sheep Am J Physiol Heart Circ Physiol, December 1, 2006; 291(6): H2884 - H2888. [Abstract] [Full Text] [PDF]

				G. D. Giraud, J. J. Faber, S. Jonker, L. Davis, and D. F. Anderson Intravascular infusions of plasma into fetal sheep cause arterial and venous hypertension J Appl Physiol, September 1, 2005; 99(3): 884 - 889. [Abstract] [Full Text] [PDF]

				J. Faber, D. Anderson, R. Hohimer, Q. Yang, G. Giraud, and L. Davis Function curve of the membranes that regulate amniotic fluid volume in sheep Am J Physiol Heart Circ Physiol, July 1, 2005; 289(1): H146 - H150. [Abstract] [Full Text] [PDF]

				M. V. Donoso, R. Lopez, R. Miranda, R. Briones, and J. P. Huidobro-Toro A2B adenosine receptor mediates human chorionic vasoconstriction and signals through arachidonic acid cascade Am J Physiol Heart Circ Physiol, May 1, 2005; 288(5): H2439 - H2449. [Abstract] [Full Text] [PDF]

				J. P. H. M. van den Wijngaard, A. Umur, R. T. Krediet, M. G. Ross, and M. J. C. van Gemert Modeling a hydropic recipient twin in twin-twin transfusion syndrome Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2005; 288(4): R799 - R814. [Abstract] [Full Text] [PDF]

				E. R. Lumbers, A. J. Gunn, D. Y. Zhang, J. J. Wu, L. Maxwell, and L. Bennet Nonimmune hydrops fetalis and activation of the renin-angiotensin system after asphyxia in preterm fetal sheep Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2001; 280(4): R1045 - R1051. [Abstract] [Full Text] [PDF]

				A. Chlorakos, B. L. Langille, and S. L. Adamson Cardiovascular responses attenuate with repeated NO synthesis inhibition in conscious fetal sheep Am J Physiol Heart Circ Physiol, May 1, 1998; 274(5): H1472 - H1480. [Abstract] [Full Text] [PDF]

				J. R. Kaiser, B. E. Cox, T. A. Roy, and C. R. Rosenfeld Differential development of umbilical and systemic arteries. I. ANG II receptor subtype expression Am J Physiol Regulatory Integrative Comp Physiol, March 1, 1998; 274(3): R797 - R807. [Abstract] [Full Text] [PDF]