Placental calcium transport during acute maternal hypermagnesemia in the rat.
OBJECTIVE
Our aim was to test the hypothesis that maternofetal placental calcium transfer rate decreases in experimentally induced acute maternal hypermagnesemia in the rat.


METHODS
We measured the unidirectional maternofetal clearance of calcium 45 and chromium 51-ethylenediaminetetraacetic acid across in situ perfused placentas of rats randomized to intravenous treatment with saline solution and magnesium sulfate (n = 5) or to saline solution only (n = 5) before placental perfusion. The maternofetal clearance of chromium 51-ethylenediaminetetraacetic acid provides a measure of placental "porosity" or passive permeability.


RESULTS
The mean serum magnesium concentration increased to 5.3 +/- 0.6 mg/dl (2.18 +/- 0.25 mmol/L) in magnesium-infused rats, staying at 1.8 +/- 0.1 mg/dl (0.74 +/- 0.04 mmol/L) in control rats (p < 0.001). Neither the maternofetal clearance of calcium 45 nor that of chromium 51-ethylenediaminetetraacetic acid was affected by acute maternal hypermagnesemia.


CONCLUSIONS
Within the range of hypermagnesemia studied, placental calcium transport remains unaffected.
Mimouni
F
F
Department of Pediatrics, University of Pittsburgh School of Medicine, PA.
Mughal
Z
Z
Hammond
G
G
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002860:Chromium Radioisotopes; D004492:Edetic Acid; D005260:Female; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000097:blood*; D008431:Maternal-Fetal Exchange; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley
D002132:Calcium Radioisotopes; D002860:Chromium Radioisotopes; D004492:Edetic Acid; D008274:Magnesium; D002118:Calcium