Distribution of ionic sulfate, lithium, and bromide across the sheep placenta

K. L. Thornburg, N. D. Binder, J. J. Faber

    Research output: Contribution to journalArticle

    15 Scopus citations

    Abstract

    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.

    Original languageEnglish (US)
    Pages (from-to)C58-C65
    JournalAmerican Journal of Physiology - Cell Physiology
    Volume5
    Issue number1
    DOIs
    StatePublished - 1979

    ASJC Scopus subject areas

    • Physiology
    • Cell Biology

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