title: Development of passive permeability characteristics of rat placenta during the last third of gestation.
abstract: To investigate how the passive permeability of the rat placenta changes during the last third of gestation we measured the unidirectional maternofetal clearance (Kmf) of three polar nonelectrolytes. We found that Kmf (microliters.min-1.g placenta-1) for all three tracers increased between days 15 and 22 (term is 23 days). The increase was less for the largest tracer, [14C]inulin (3.5-fold increase from 0.5 +/- 0.1 to 1.6 +/- 0.1 microliters.min-1.g placenta-1), than for the smaller tracers, [14C]mannitol (7-fold increase from 1.6 +/- 0.1 to 10.9 +/- 0.4 microliters.min-1.g placenta-1) and 51Cr-labeled EDTA (9.5-fold increase from 0.8 +/- 0.04 to 7.6 +/- 0.7 microliters.min-1.g placenta-1). These data suggest that whilst the overall permeability of the rat placenta increases during this period of pregnancy, restriction to the diffusion of large (greater than or equal to 1.5 nm molecular radius) polar nonelectrolytes also increases.
authors.affiliation: Department of Child Health, The University of Manchester, St. Mary's Hospital, United Kingdom.
authors.forename: D E
authors.initials: DE
authors.lastname: Atkinson
authors.forename: N R
authors.initials: NR
authors.lastname: Robinson
authors.forename: C P
authors.initials: CP
authors.lastname: Sibley
mesh_terms: D000818:Animals; D001835:Body Weight; D002250:Carbon Radioisotopes; D002860:Chromium Radioisotopes; D004492:Edetic Acid / Q000378:metabolism; D005260:Female; D005333:Fetus; D007444:Inulin / Q000378:metabolism; D008353:Mannitol / Q000378:metabolism; D009929:Organ Size; D010539:Permeability; D010920:Placenta / Q000033:anatomy & histology / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D002250:Carbon Radioisotopes; D002860:Chromium Radioisotopes; D008353:Mannitol; D007444:Inulin; D004492:Edetic Acid