Concentrations of Na+ and Cl- in transplacental ultrafiltrate in sheep.
1. Maternal blood was made transiently hypertonic by rapid I.V. infusion of a concentrated mannitol solution into pregnant ewes bearing lambs with an indwelling flow sensor and vascular catheters. 2. The transplacental flows of water and of Na+ and Cl- were calculated from the umbilical arteriovenous differences in the concentrations of 125I-labelled albumin and electrolytes, and the fetal placental blood flow. 3. The reflection coefficients of Na+ and Cl- were calculated by means of the Patlak equation and found to be 0.85 +/- 0.04 and 0.68 +/- 0.04 (means +/- S.E.M.). The filtration coefficient was 1.02 x 10(-7) +/- 0.12 x 10(-7) cm5 dyne-1 s-1. 4. The results fitted best to an equivalent pore radius in the placental barrier smaller than the currently accepted 0.44 nm but not less than 0.35 nm.
D000818:Animals; D001158:Arteries; D002712:Chlorides / Q000378:metabolism*; D005260:Female; D005333:Fetus / Q000502:physiology; D005740:Gases / Q000097:blood; D006982:Hypertonic Solutions / Q000494:pharmacology; D008431:Maternal-Fetal Exchange; D009994:Osmolar Concentration; D010920:Placenta / Q000098:blood supply / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D012756:Sheep; D012964:Sodium / Q000378:metabolism*; D014462:Ultrafiltration; D014680:Veins
D002712:Chlorides; D005740:Gases; D006982:Hypertonic Solutions; D012964:Sodium