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Title: Passive permeability of the human placenta 'in-vivo'
Author: Bain, Murray D.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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Transfer across the placenta between mother and foetus underlies normal foetal growth and development. Although passive diffusion is the simplest of the several mechanisms of transfer and despite its potential importance for foetal growth, there have been few 'in-vivo' measurements of passive permeability in the human. To provide such data passive permeability was measured 'in-vivo' in 13 pregnancies scheduled for delivery by elective casesarean section. Four different sized, inerts, and hydrophilic, molecular permeants were used; mannitol, lactulose, CrEDTA, and inulin. A bolus and constant infusion were used to create a maternal-foetal concentration gradient. The subsequent neonatal urinary excretion of the permeants was measured and equalled the net transfer to the foetus as the permeants were cleared wholly and solely by renal excretion. The passive permeability of the placenta was calculated by dividing the net flux by the mean transplacental concentration gradient. Permeability measurements for mannitol and inulin were undertaken in 6 pregnancies, and for all four permeants in 7 pregnancies. Placental clearance (passive permeability of the whole placenta) was (mean ± S.E. of mean) 8.1 ± 0.7 ml.min-1 for mannitol, 6.3 ± 0.8 for lactulose, 3.7 ± 0.5 for CrEDTA, and 0.92 ± 0.07 for mannitol. The corresponding passive permeabilities per unit weight placenta were 13.52 ± 1.32 x 10-3 ml.min-1.g-1 for mannitol, 10.844 ± 1.55 x 10^-3 for lactulose, 6.33 ± 0.84 x 10-3 for CrEDTA and 1.53 ± 0.11 x 10^-3 for inulin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available