AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 6 1431-R1435, Copyright © 1990 by American Physiological Society
Cardiovascular changes after closure of uterine circulation during pregnancy
G. J. Valenzuela, S. Kim and H. F. Rauld
Division of Perinatal Biology, Loma Linda University, California 92350.
To assess the effects of the presence of the uteroplacental circulation on
the systemic arterial pressure, blood volume, and cardiac output during
pregnancy, we measured those variables and plasma renin activity (PRA)
during a 30-min period before and after occlusion of the uterine
circulation. After uterine vascular occlusion, pregnant rabbits (n = 7)
experienced a drop in mean arterial pressure of 8.7%, heart rate of 9.5%,
cardiac output of 30.2%, and hematocrit of 18.2% (each with P less than
0.05). Stroke volume decreased an average of 29.7%; however, it did not
reach significance. PRA and venous pressure did not change significantly
from the control period (P greater than 0.1). Nonpregnant rabbits did not
experience changes in arterial or venous pressures, hematocrit, heart rate,
cardiac output, or PRA after closure of the uterine circulation. To exclude
the possibility that the findings were secondary to the release of toxic
products to the peritoneal cavity by the ischemic pregnant uterus, we also
studied the effect of closure of the uterine circulation in five
anesthetized pregnant guinea pigs. These animals' uteri were exteriorized
and maintained in a sealed plastic container during the experiment. In
these animals, arterial pressure decreased 15.6% by 10 min (P less than
0.05). The finding of a significant decrease in arterial pressure and heart
rate is compatible with the idea that the uterine circulation produces a
substance with a short half-life that has a significant direct effect on
the heart and/or systemic vascular tone.
