Inhibitor action on placental calcium transport.
Human term placental lobules were dually perfused with Krebs Ringer solution at 37 degrees C under open circuit conditions. Provided that perfusate Ca2+ concentrations were between 2.33 and 2.55 mM, there was a steady release of Ca2+ into the fetal circulation and uptake of Ca2+ from the maternal circulation. There was no significant calcium (Ca) protein binding in the perfusates. Addition of dinitrophenol altered the release of Ca2+ to an uptake on the fetal circuit and enhanced Ca2+ uptake on the maternal circuit. It also produced a release of potassium (K)+ and an uptake of Na+ on both sides of the placenta. Ouabain had no significant effect on Ca movements although it produced a marked release of K+ into the fetal perfusate. The effect of cooling on the fetal circuit was similar to that of dinitrophenol (DNP), although it did not produce significant changes in either Ca2+ or K+ movements on the maternal side of the lobule. Both DNP and cooling reduced the Ca concentration ratio between fetal and maternal outflows to unity. Replacement of Na+ by choline Ringer had only transient effect on the extraction of 45Ca from fetal perfusate. These observations indicate that a Ca2+/Na (sodium)+ exchanger does not make a major contribution to the transplacental movement of Ca2+ from mother to fetus and that this process is more probably associated with membrane-bound ATPases.
Williams
J M
JM
Department of Anatomy, University of Aberdeen, Marischal College, United Kingdom.
Abramovich
D R
DR
Dacke
C G
CG
Mayhew
T M
TM
Page
K R
KR
D000251:Adenosine Triphosphatases / Q000502:physiology; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000097:blood / Q000493:pharmacokinetics*; D002132:Calcium Radioisotopes; D002352:Carrier Proteins / Q000502:physiology; D002794:Choline / Q000378:metabolism; D004140:Dinitrophenols / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008431:Maternal-Fetal Exchange / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology*; D010477:Perfusion; D010920:Placenta / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D011247:Pregnancy; D012964:Sodium / Q000378:metabolism / Q000493:pharmacokinetics; D019831:Sodium-Calcium Exchanger; D013696:Temperature
D002132:Calcium Radioisotopes; D002352:Carrier Proteins; D004140:Dinitrophenols; D008565:Membrane Proteins; D019831:Sodium-Calcium Exchanger; D010042:Ouabain; D012964:Sodium; D000251:Adenosine Triphosphatases; D002794:Choline; D011188:Potassium; D002118:Calcium