TY - JOUR
T1 - Distribution of ionic sulfate, lithium, and bromide across the sheep placenta
AU - Thornburg, K. L.
AU - Binder, N. D.
AU - Faber, J. J.
PY - 1979
Y1 - 1979
N2 - Salts of sulfate, lithium, and bromine were injected or infused intravenously into ewes in the last trimester of gestation. Ewes and fetuses had indwelling catheters, most fetuses were nephrectomized. Concentrations were measured in paired maternal and fetal samples over periods of 4-14 days. Maternal excretion of sulfate was too rapid to permit near equilibration of fetal and maternal plasma concentrations; the results, however, did not support the existence of a large potential difference across the exchange barrier. The concentrations of Li+ (given by continuous infusion) and 82Br- in maternal plasma did not change rapidly. The concentrations of these tracers in fetal plasma rose until they were nearly equal to the maternal plasma concentrations. Steady-state transplacental potentials, calculated by use of the Nernst equation, were 5.2 ± 2.0 (SEM) mV (n = 26) for Li+ and -2.2 ± 0.8 (SEM) mV (n = 10) for Br-. Nernst potentials calculated from previously measured maternal and fetal plasma concentrations of Na+, K+, Mg2+, and Cl- were +0.4, +3.6, +0.5, and -1.4 mV. The authors concluded that, of the total potential difference of about -50 mV (fetus negative) between the fetal lamb and the ewe, only a few mV are dropped across the placental exchange barrier.
AB - Salts of sulfate, lithium, and bromine were injected or infused intravenously into ewes in the last trimester of gestation. Ewes and fetuses had indwelling catheters, most fetuses were nephrectomized. Concentrations were measured in paired maternal and fetal samples over periods of 4-14 days. Maternal excretion of sulfate was too rapid to permit near equilibration of fetal and maternal plasma concentrations; the results, however, did not support the existence of a large potential difference across the exchange barrier. The concentrations of Li+ (given by continuous infusion) and 82Br- in maternal plasma did not change rapidly. The concentrations of these tracers in fetal plasma rose until they were nearly equal to the maternal plasma concentrations. Steady-state transplacental potentials, calculated by use of the Nernst equation, were 5.2 ± 2.0 (SEM) mV (n = 26) for Li+ and -2.2 ± 0.8 (SEM) mV (n = 10) for Br-. Nernst potentials calculated from previously measured maternal and fetal plasma concentrations of Na+, K+, Mg2+, and Cl- were +0.4, +3.6, +0.5, and -1.4 mV. The authors concluded that, of the total potential difference of about -50 mV (fetus negative) between the fetal lamb and the ewe, only a few mV are dropped across the placental exchange barrier.
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U2 - 10.1152/ajpcell.1979.236.1.c58
DO - 10.1152/ajpcell.1979.236.1.c58
M3 - Article
C2 - 434139
AN - SCOPUS:0018344928
VL - 5
SP - C58-C65
JO - American Journal of Physiology
JF - American Journal of Physiology
SN - 0363-6143
IS - 1
ER -