Sodium-dependent magnesium transport across in situ perfused rat placenta.
Placentas of anesthetized rats were perfused in situ on the fetal side to study mechanisms of Mg2+ transport. The perfusate was a Mg(2+)-free Krebs-Ringer, and the unidirectional transfer of Mg2+ from maternal plasma to this Ringer was compared with that of 45Ca and 51Cr-EDTA, the latter being employed as a paracellular diffusional marker. Placental perfusion with amiloride (0.5 mM) or ouabain (1 mM) both rapidly (4 min) reduced maternal-fetal clearance (Kmf) for Mg2+ but had no effect on Kmf for 45Ca. In contrast, perfusion of the carbonic anhydrase inhibitor acetazolamide (1 mM) did not affect Kmf for Mg2+ or 45Ca. Placental perfusion with a Na+-free Ringer reduced Kmf for both Mg2+ and 45Ca, although the latter response was delayed. Kmf for 51Cr-EDTA was increased by amiloride and was unaffected by perfusion of ouabain, acetazolamide, or Na+-free Ringer, indicating that the effects of these treatments on Kmf of Mg2+ do not reflect nonspecific effects on placental permeability. These data suggest that maternal-fetal transfer of Mg2+ across the perfused rat placenta is Na+ dependent.
Shaw
A J
AJ
Department of Child Health, St. Mary's Hospital, University of Manchester, United Kingdom.
Mughal
M Z
MZ
Maresh
M J
MJ
Sibley
C P
CP
D000086:Acetazolamide / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000493:pharmacokinetics; D002794:Choline / Q000494:pharmacology; D004492:Edetic Acid / Q000493:pharmacokinetics; D005260:Female; D008274:Magnesium / Q000493:pharmacokinetics; D010042:Ouabain / Q000494:pharmacology; D010477:Perfusion; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000502:physiology*
D010042:Ouabain; D000584:Amiloride; D004492:Edetic Acid; D012964:Sodium; D008274:Magnesium; D002794:Choline; D000086:Acetazolamide; D002118:Calcium