AJP - Renal Physiology, Vol 259, Issue 6 945-F949, Copyright © 1990 by American Physiological Society
Renal effects of moderate hemorrhage in the conscious pregnant rat
C. Baylis, C. Brango and K. Engels
Department of Physiology, West Virginia University, Morgantown 26506.
Studies were performed in conscious, chronically catheterized virgin, 8- to
9-day-pregnant, and 15- to 16-day-pregnant Sprague-Dawley rats in baseline
state and after removal of 7.5% total blood volume. Measurements were made
of glomerular filtration rate (GFR), renal plasma flow (RPF), renal
vascular resistance (RVR), arterial blood pressure (AP), and urinary
electrolyte excretion. In baseline state, GFR and RPF were elevated at days
8-9 and days 15-16 of pregnancy (vs. virgins) due to a gestational renal
vasodilation. The fall in hematocrit indicates substantial plasma volume
expansion by days 15-16 of pregnancy. After removal of 7.5% total blood
volume, little change occurred in AP in any group. However, the renal
vasculature provided a sensitive response to moderate hemorrhage, since RPF
fell and RVR increased similarly in virgin, 8- to 9-day- and 15- to
16-day-pregnant rats. GFR was protected in virgin and 8- to 9-day-pregnant
rats but fell significantly in late pregnancy. Urinary electrolyte
excretion tended to fall but was not significantly reduced by hemorrhage in
any group. These studies indicate that renal vascular response to moderate
hemorrhage is similar in virgin, early, and late pregnancy. Thus effector
mechanisms that sense volume and regulate RVR must be continually reset to
respond to progressive plasma volume expansion of pregnancy as normal.
