Transplacental clearance and blood flows of bovine gravid uterus at several stages of gestation
Rates of uterine and umbilical blood flows and transplacental clearance of deuterium oxide (D/sub 2/O) were determined for cows on 137 +/- 1.0 (SE, n = 9), 180 +/- 0.5 (n = 8), 226 +/- 0.4 (n = 9), and 250 +/- 1.8 (n = 5) days of gestation. From days 137 to 250, rates increased 4.5-fold for uterine blood flow, 21-fold for umbilical blood flow, and 14-fold for clearance of D/sub 2/O. Changes in rates of umbilical blood flow and D/sub 2/O clearance paralleled increased rates of fetal growth and metabolism, which have previously been reported to occur during the last half of gestation. The regressions of D/sub 2/O clearance on uterine and umbilical blood flows were significant (P less than 0.01) and explained 94-99% of the variation in placental clearance of D/sub 2/O. Because the rate of D/sub 2/O clearance was always less than that of uterine and umbilical blood flows, and because a relatively simple statistical model explained most of the variation in clearance, it was suggested that a concurrent or countercurrent arrangement of maternal and fetal placental microvasculatures is not adequate to explain clearance of highly diffusable substances across the bovine placenta. In addition, a placental exchange diagram of the data showed the existence of severe uneven distribution of maternal and fetal placental blood flows and/or significant shunting of maternal and fetal placental flows away from areas of exchange. Taken together, these data indicate that the placenta of the cow, like those of the sheep and goat, represents a relatively inefficient system of transplacental exchange.
- Research Organization:
- North Dakota State Univ., Fargo
- OSTI ID:
- 5650997
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 253
- Country of Publication:
- United States
- Language:
- English
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UTERUS
BLOOD FLOW
ANTIPYRINE
BLOOD
CATTLE
CLEARANCE
DEUTERIUM
MEMBRANE TRANSPORT
PLACENTA
PREGNANCY
TRACER TECHNIQUES
ANIMALS
ANTIPYRETICS
AZOLES
BIOLOGICAL MATERIALS
BODY
BODY FLUIDS
CENTRAL NERVOUS SYSTEM DEPRESSANTS
DOMESTIC ANIMALS
DRUGS
FEMALE GENITALS
FETAL MEMBRANES
HETEROCYCLIC COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MAMMALS
MATERIALS
MEMBRANES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PYRAZOLES
PYRAZOLINES
RUMINANTS
STABLE ISOTOPES
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques