Theoretical and experimental study of transplacental diffusion

Meschia, Giacomo; Battaglia, Frederick C.; Bruns, Paul D.

doi:10.1152/jappl.1967.22.6.1171

Cited by 136 publications

(55 citation statements)

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“…However, there is always inequality of concentrations in the main uterine and umbilical veins. As shown in Figure 6, the umbilical vein-to-uterine vein concentration difference for molecules with flow-limited transplacental clearance (e.g., antipyrine and tritiated water) averages 18% of the umbilical artery-to-uterine artery difference (14). The data obtained from three studies (present report, 13 and 14) permit a calculation of the umbilical and uterine venous concentration differences for antipyrine or tritiated water before admixture with noncotyledonary venous blood.…”

Section: Discussionmentioning

confidence: 59%

“…In experiments with the steadystate diffusion of inert molecules from fetus to mother, we have shown that the sheep placenta simulates a concurrent exchange system in which the concentrations of the diffusing substance in the veins of the donor and recipient streams tend to equilibrate (5,14). However, there is always inequality of concentrations in the main uterine and umbilical veins.…”

Section: Discussionmentioning

confidence: 98%

“…Thus, there is a residual inefficiency of placental exchange within the cotyledons when compared to an ideal concurrent exchange system. This inefficiency could be the result of uneven perfusion ratios and intracotyledonary shunts (14). Experimental evidence (15,16) favors this hypothesis.…”

Section: Discussionmentioning

confidence: 98%

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Measurement of Umbilical Arterial Blood Flow to the Sheep Placenta and Fetus in Utero

Makowski

Meschia

Droegemueller

et al. 1968

Circulation Research

197

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A method of estimating the magnitude and distribution of umbilical blood flow by means of radioactive microspheres in sheep fetuses in utero is described. Simultaneous measurements of total umbilical flow by this method and the steady-state diffusion technique showed agreement within ± 11%. In 11 fetuses of 90 to 150 days gestational age, the distribution of umbilical flow to the intercotyledonary chorion was 6.2 ± 0.8% of the total. This information has been used to estimate the effect of venous admixture of cotyledonary and noncotyledonary blood on the umbilical vein-uterine vein concentration difference of inert molecules with flow-limited transplacental clearance. ADDITIONAL KEY WORDSradioactive microspheres antipyrine regional blood flows shunted blood flow transplacental diffusion• Several methods of measuring umbilical blood flow of lamb fetuses have been described (1-6). Electromagnetic flowmeters placed in the common umbilical vein give a precise and continuous recording of umbilical blood flow, but the flows in such circumstances may be abnormal because the fetus is exteriorized and subjected to considerable surgical trauma. To avoid these disadvantages, methods of determining umbilical flow of the fetus within the uterine cavity have been developed. Accepted for publication September 9, 1968. is infused at a constant rate in a fetal vein until the transplacental diffusion rate of the test substance becomes constant. Umbilical flow can then be calculated as the ratio of the transplacental diffusion rate over the arteryto-vein difference of the test substance in the umbilical circulation. The validity of the calculated flow depends primarily on an accurate estimate of the transplacental diffusion rate and on the assumption that the umbilical vein sample is representative of total umbilical outflow. A comparison in the exteriorized fetus of the steady-state diffusion method with the cannulating electromagnetic flowmeter method has shown satisfactory agreement (7), but there has been no comparison of two independent intrauterine methods. The umbilical circulation of the sheep fetus is distributed to two structures: (1) the placental cotyledons and (2) the intercotyledonary chorion. In the cotyledons, maternal and fetal capillaries are in close apposition over a relatively large surface area, while in the intercotyledonary chorion the two capillary beds are separated by a greater

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Section: Discussionmentioning

confidence: 59%

Section: Discussionmentioning

confidence: 98%

See 1 more Smart Citation

Measurement of Umbilical Arterial Blood Flow to the Sheep Placenta and Fetus in Utero

Makowski

Meschia

Droegemueller

et al. 1968

Circulation Research

197

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“…It has been previously shown that antipyrine and water clearances are not significantly different in perfused human placenta or in sheep cotyledon (Meschia et al, 1967 …”

mentioning

confidence: 95%

“…The disposition of blood streams also intervenes when the membrane is interposed between two circulations, as in the case of the placenta. In some typical blood stream arrangements, a specific relationship exists between transfer and flow rate Meschia et al, 1967). Thus, crosscurrent and countercurrent exchangers have been ascribed to sheep (Rankin and Peterson, 1969) and to guinea-pig (Moll and Kastendieck, 1977) Hart (1966) andFaber (1969) The antipyrine in these samples, along with that in arterial perfusate samples, was separated by serial chloroform extraction.…”

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confidence: 99%