Transplacental clearance and blood flows of bovine gravid uterus at several stages of gestation

1987 ◽  
Vol 253 (5) ◽  
pp. R735-R739 ◽  
Author(s):  
L. P. Reynolds ◽  
C. L. Ferrell
Keyword(s):  
Blood Flow ◽  
Statistical Model ◽  
Deuterium Oxide ◽  
Gravid Uterus ◽  
Uterine Blood Flow ◽  
Blood Flows ◽  
Bovine Placenta ◽  
Umbilical Blood ◽  
Placental Blood ◽  
Umbilical Blood Flow

Rates of uterine and umbilical blood flows and transplacental clearance of deuterium oxide (D2O) 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 D2O. Changes in rates of umbilical blood flow and D2O 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 D2O 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 D2O. Because the rate of D2O 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.

Metabolism of the gravid uterus, foetus and utero-placenta at several stages of gestation in cows

1986 ◽  
Vol 106 (3) ◽  
pp. 437-444 ◽  
Author(s):  
L. P. Reynolds ◽  
C. L. Ferrell ◽  
Debra A. Robertson ◽  
S. P. Ford
Keyword(s):  
Blood Flow ◽  
Deuterium Oxide ◽  
N Uptake ◽  
Gravid Uterus ◽  
Uterine Blood Flow ◽  
Indwelling Catheters ◽  
Blood Flows ◽  
Umbilical Blood ◽  
Rate Of Increase ◽  
Umbilical Blood Flow

SummaryTo quantify changes in rates of metabolism and nutrient uptake of gravid uteiine, foetal and utero-placental tissues throughout gestation, mature Hereford cows received surgery at 132 ± 0·6 (n = 12), 176 ± 0·5 (n = 8), 220 ±0·4 (n = 11) and 245 ±1·5 (n = 7) days after mating. Indwelling catheters were implanted into a uterine artery and vein of all cows. Foetal catheters also were implanted into an umbilical vein and foetal femoral artery and vein (days 176 and 220) or into a placental artery and two placental veins (days 132 and 245). Approximately 5 days after surgery, deuterium oxide was infused into a foetal femoral venous or placental venous catheter during a 3 h period to quantify uterine and umbilical blood flows by steady-state diffusion methods. Oxygen, glucose, lactate and α-amino acid nitrogen concentrations were determined for uterine and foetal blood samples collected during this procedure.Uterine blood flow increased 4·5-fold (2·92–13·181/min) and umbilical blood flow increased 21-fold (0·28–5·861–min) during the interval of gestation studied. The relative rate of increase of umbilical blood flow was about twice as great as that of uterine blood flow. Uterine arterial and umbilical venous concentrations as well as uterine arterial-venous and umbilical venous-arterial concentration differences in metabolites changed little with stage of gestation. However, because rates of blood flow increased, uptakes of O2, glucose and α-amino N by the gravid uterus and foetus increased as gestation advanced. The proportion of gravid uterine uptakes utilized by the foetus increased from day 137 to 226 for O2 (24–58%) and from day 137 to 180 for glucose (4–19%), then remained relatively constant. The proportion of gravid uterine α-amino N uptake utilized by the foetus remained relatively constant and averaged 60%. A net secretion of lactate from the utero-placenta to the uterine and foetal circulations was observed and increased as gestation advanced. These data indicate that increased rates of uptake or secretion of metabolites by tissues of the gravid uterus can be explained primarily by increased rates of uterine and umbilical blood flows.

Effect of restriction of placental growth on umbilical and uterine blood flows

1986 ◽  
Vol 250 (3) ◽  
pp. R427-R434 ◽  
Author(s):  
J. A. Owens ◽  
J. Falconer ◽  
J. S. Robinson
Keyword(s):  
Blood Flow ◽  
Subsequent Pregnancy ◽  
Placental Weight ◽  
Fetal Weight ◽  
Uterine Blood Flow ◽  
Antipyrine Clearance ◽  
Blood Flows ◽  
Umbilical Blood ◽  
Umbilical Blood Flow ◽  
Vascular Catheters

Endometrial caruncles were excised from sheep (caruncle sheep) before pregnancy. The effect of this on umbilical and uterine blood flows in a subsequent pregnancy was examined. Thirteen caruncle and twelve control sheep with indwelling vascular catheters were studied at 121 and 130 days pregnancy. In caruncle sheep, fetal, placental, and total uterine content weights were significantly lower than in control sheep. Six caruncle sheep carried normal-sized fetuses (weight within +/- 2 SD of mean weight for control fetuses) and seven carried small fetuses (weight greater than +/- 2 SD below mean weight for control fetuses). Mean weights of placentas in these groups were 0.290 +/- 0.067 and 0.156 +/- 0.069 kg, respectively, compared with 0.459 +/- 0.157 kg in control sheep. In small caruncle fetuses, umbilical and uterine blood flows and placental antipyrine clearance were significantly lower than in controls at 121 and 130 days gestation. Only umbilical blood flow was reduced in normal-sized caruncle fetuses. Umbilical blood flow and placental antipyrine clearance increased with gestational age in control sheep but not in sheep with normal-sized or small caruncle fetuses. In all sheep, umbilical and uterine blood flows and antipyrine clearance correlated with placental weight. Umbilical blood flow per kilogram of placenta but not uterine blood flow per kilogram of placenta correlated inversely with placental weight. Fetal weight at 130 days generally correlated with placental weight, umbilical and uterine blood flows, and antipyrine clearance in a curvilinear fashion such that fetal weight was not greatly restricted until these variables were less than or equal to 65% of control values.

Placental transfer as a function of uterine blood flow

1982 ◽  
Vol 242 (3) ◽  
pp. H429-H436 ◽  
Author(s):  
R. B. Wilkening ◽  
S. Anderson ◽  
L. Martensson ◽  
G. Meschia
Keyword(s):  
Blood Flow ◽  
Placental Transfer ◽  
Appreciable Effect ◽  
Uterine Blood Flow ◽  
Placental Perfusion ◽  
Umbilical Blood ◽  
Norepinephrine Infusion ◽  
Umbilical Blood Flow ◽  
Clearance Level ◽  
Different Levels

The effect of variations of uterine blood flow (F) on placental transfer was examined in six chronic sheep preparations by measuring the placental clearances of ethanol (CE) and antipyrine (CA) at different levels of F. Norepinephrine infusion, hemorrhage, and occlusion of the terminal aorta were used to reduce F below normal. The reduction of F had no appreciable effect on umbilical blood flow (f). In each ewe, CE significantly correlated with F. The CE vs. F relationship at constant f was curvilinear with convexity toward the clearance axis. Regression analysis showed that the equation 1/CE = 1/.911 F + 1/.831 f could account for most of the CE variance (r2 = 0.97). Implicit in this relation is the concept that, given a certain level of placental perfusion, an F/f ratio congruent to 1 is optimal for the exchange of highly diffusible inert molecules between mother and fetus [CE/(F + f) was maximum at F/f = 0.955]. CA was not significantly different from CE at low clearance level but became smaller than CE at clearance values greater than 300 ml/min. This suggests that a high rates of perfusion placental permeability was a factor in limiting CA.

Oxygen, glucose, and lactate uptake by fetus and placenta during prolonged hypoxemia

1995 ◽  
Vol 268 (2) ◽  
pp. R303-R309 ◽  
Author(s):  
S. B. Hooper ◽  
D. W. Walker ◽  
R. Harding
Keyword(s):  
Blood Flow ◽  
Glucose Uptake ◽  
Lactate Clearance ◽  
Gravid Uterus ◽  
Uterine Blood Flow ◽  
Fetal Circulation ◽  
Umbilical Blood ◽  
Pregnant Sheep ◽  
Lactate Uptake ◽  
Arterial O2 Saturation

Our aim was to compare the effects of short (4 h) and prolonged (24 h) periods of reduced uterine blood flow (RUBF) on fetal and placental uptake of O2, glucose, and lactate. In pregnant sheep, uterine and umbilical blood flows were measured under normal conditions and after 4 and 24 h of RUBF. A 50% reduction in uterine blood flow caused a 56% reduction in fetal arterial O2 saturation (SaO2). Umbilical blood flow increased from 325 +/- 33 to 378 +/- 32 ml.min-1.kg-1 (P < 0.05) after 4 h but was not different from pre-RUBF values after 24 h. O2 uptake by the gravid uterus was not altered by RUBF, due to an increase (84%) in uterine O2 extraction. Similarly, uteroplacental and fetal O2 consumptions and fetal glucose uptake were not affected by RUBF, whereas uteroplacental glucose uptake was significantly reduced after 4 h (by 42%) and 24 h (by 58%) of RUBF. Fetal lactate uptake was greatly reduced from 78.7 +/- 15.5 to -167 +/- 57 mumol.min-1.kg-1 after 4 h and to -198 +/- 80 mumol.min-1.kg-1 after 24 h of RUBF; negative values indicate placental lactate uptake from the fetal circulation. Thus, although RUBF significantly reduced fetal SaO2, fetal and uteroplacental O2 consumptions did not change. In addition, although fetal glucose uptake was not altered by RUBF, during RUBF the placenta became a major site of lactate clearance from the fetal circulation.

scholarly journals Effects of undernutrition and exercise during late pregnancy on uterine, fetal and uteroplacental metabolism in the ewe

1985 ◽  
Vol 53 (3) ◽  
pp. 625-635 ◽  
Author(s):  
K. D. Chandler ◽  
B. J Leury ◽  
A. R. Bird ◽  
A. W. Bell
Keyword(s):  
Blood Flow ◽  
Live Weight ◽  
Late Pregnancy ◽  
Uterine Blood Flow ◽  
Pregnant Uterus ◽  
Energy Demands ◽  
Umbilical Blood ◽  
Net Uptake ◽  
Chronic Undernutrition ◽  
Umbilical Blood Flow

1. Uterine, umbilical and, by difference, uteroplacental net uptakes of oxygen, glucose, lactate and 3-hydroxybutyrate (uterine uptake only) were measured in single-pregnant ewes which were either well-fed throughout, or severely undernourished for 8–20 d during late pregnancy. All animals were studied while standing at rest and then while walking on a treadmill at 0.7 m/s on a 10° slope for 60 min.2. Undernutrition did not significantly affect fetal or placental weights at 143 d gestation but caused a 14% decrease in maternal live weight. Uterine blood flow was decreased by 32% and was associated with a significant decrease in uteroplacental oxygen uptake; neither umbilical blood flow nor fetal O2, uptake were affected by maternal plane of nutrition. Maternal and fetal hypoglycaemia in underfed ewes was accompanied by 46–63 % decreases in uterine, umbilical and uteroplacental net uptakes of glucose, and similar declines in uterine and umbilical glucose/O, quotients. Moderate maternal hyperketonaemia was associated with 2.5-fold and 3-fold increases in uterine net uptake of 3-hydroxybutyrate and 3-hydroxybutyrate/O2 quotient respectively.3. Exercise caused significant decreases in uterine blood flow in fed and underfed ewes but did not affect uterine or umbilical O2 uptakes; uterine net glucose uptake increased in most ewes but umbilical uptake was not significantly affected. Umbilical net uptake of lactate was significantly reduced. In underfed ewes, the extent of hyperketonaemia was significantly reduced by exercise.4. Contrary to earlier proposals, the ovine pregnant uterus is sensitive and adaptable to long- and short-term alterations in maternal energy balance, as achieved by chronic undernutrition and exercise respectively. Thus, the fetus and placenta significantly add to, but do not necessarily have priority over the energy demands of other tissues of the ewe.

Fetal neuromuscular blockade: effect on oxygen demand and placental transport

1989 ◽  
Vol 257 (3) ◽  
pp. H734-H738
Author(s):  
R. B. Wilkening ◽  
D. W. Boyle ◽  
G. Meschia
Keyword(s):  
Blood Flow ◽  
Oxygen Saturation ◽  
Neuromuscular Blockade ◽  
Umbilical Vein ◽  
Oxygen Demand ◽  
Arterial Oxygen ◽  
Uterine Blood Flow ◽  
Umbilical Blood ◽  
Steady State Method ◽  
Umbilical Blood Flow

To study mechanisms by which variations in fetal oxygen demand alter fetal oxygen saturation and PO2, we measured uterine and umbilical blood flow and transplacental oxygen diffusion rate in eight chronically prepared pregnant ewes before and during fetal neuromuscular blockade with pancuronium bromide (0.2 mg/kg). Uterine and umbilical blood flows were measured by applying the steady-state method using ethanol as the test substance. Fetal oxygen uptake decreased 7.5% (P less than 0.05). Umbilical blood flow increased 6% (P less than 0.05), whereas uterine blood flow did not change significantly. Fetal arterial oxygen saturation increased markedly (54.8–60.9%; P less than 0.001). There were also significant increases in umbilical vein oxygen saturation (83.6–86.9%; P less than 0.01), uterine vein oxygen saturation (70.7–72.2%; P less than 0.01), umbilical vein PO2 (29.4–32.1 Torr; P less than 0.001), and uterine vein PO2 (49.4–50.7 Torr; P less than 0.01). The uterine-umbilical venous PO2 difference decreased significantly (20.0–18.6 Torr; P less than 0.001), whereas there was no significant change in the uterine-umbilical venous PCO2 difference or in the umbilical ethanol shunt. The data indicate that follows a small decrease in fetal oxygen demand is caused by two aspects of placental oxygen transport: 1) umbilical and uterine blood flow do not react homeostatically to prevent the rise of PO2 in the placental circulation, and 2) the decrease in oxygen flux from placenta to fetus is associated with a decrease in the transplacental PO2 gradient.

Absence of fetal placental waterfall phenomenon in chronically prepared fetal lambs

1976 ◽  
Vol 230 (4) ◽  
pp. 886-892 ◽  
Author(s):  
KL Thornburg ◽  
JM Bissonnette ◽  
JJ Faber
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Arterial Blood Pressure ◽  
Umbilical Vein ◽  
Venous Pressure ◽  
Amniotic Cavity ◽  
Umbilical Blood ◽  
Arterial Blood ◽  
Placental Blood ◽  
Umbilical Blood Flow

An electromagnetic flow sensor was placed on the distal fetal aorta (umbilical flow fraction 78.1 +/- 1.6 SEM, %), an inflatable occluder was tied around the umbilical cord, and catheters were placed in distal branches of an umbilical artery and vein, a uterine vein, and in the amniotic cavity. An inflatalbe occluder was tied around the vagina of some of the ewes. Control values 3 days after surgery were (mean +/- SE): fetal femoral artery pH, 7.37 +/- 0.01; umbilical blood flow, 186 +/- 14 ml-min-1 .kg fetus-1; fetal arterial blood pressure, 39 +/- 3 mmHg; and umbilical venous pressure, 7.4 +/- 1.0 mmHg (above intrauterine pressure). Fetal weight at autopsy was 3.1 +/- 0.3 kg, n = 11. Small increases in umbilical vein pressure caused immediate decreases in placental blood flow without decreases in fetal arterial blood pressure. The relation between venous pressure and umbilical blood flow at constant arterial pressure was that of an inert system, i.e., no evidence of a surrounding pressure (Starling resistor effect or waterfall phenomenon) could be found with increases in venous pressures of 2-40 mmHg. The results were not affected by increases in uterine vein pressure between 2 and 30 mmHg, nor by anesthesia and supine position of the ewe, nor by ganglionic blockade of the fetal ANS. It was concluded that surrounding pressures in the fetal placental circulation could not be demonstrated.

Effects of ovine maternal hyperglycemia on fetal regional blood flows and metabolism

1985 ◽  
Vol 249 (5) ◽  
pp. E454-E460 ◽  
Author(s):  
S. S. Crandell ◽  
D. J. Fisher ◽  
F. H. Morriss
Keyword(s):  
Blood Flow ◽  
Regional Distribution ◽  
Cardiovascular Responses ◽  
Late Gestation ◽  
Intravenous Glucose ◽  
Blood Flows ◽  
Umbilical Blood ◽  
Maternal Hyperglycemia ◽  
Regional Blood Flows ◽  
Placental Blood

Fetal combined ventricular output (CVO) and regional distribution of blood flow were measured in 12 ewes in late gestation by the radiolabeled microsphere method. Three sets of determinations were made in sequence beginning with a control study and repeating the measurements after the ewe had received intravenous glucose at 0.35 g X min-1 for 90 min and again after the ewe had received glucose at 0.85 g X min-1 for a second 90-min period. Maternal whole blood glucose concentrations were 2.98 +/- 0.18 (means +/- SE), 10.43 +/- 0.45, and 21.59 +/- 0.90 mM during the respective study periods. Fetal CVO did not change during maternal hyperglycemia; however, it was redistributed, with a decrease in umbilical blood flow to the placenta from 43.5% of CVO to 31.9 and 30.8%, respectively. The fetal carcass, heart, intestines, kidneys, liver, and adrenals each received increased percent CVO; these increases equaled the decrease in placental blood flow. Fetuses became hypoxemic and developed a mixed acidemia during induced maternal hyperglycemia, but oxygen delivery to the heart, brain, and kidneys was unchanged. These observations indicate that maternal hyperglycemia results in previously unsuspected fetal cardiovascular responses.

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