Fetal magnesium homeostasis in the sheep

The fetal plasma magnesium concentration exceeds that of the mother but the difference is small compared to that of ionized calcium concentration. Although not fully independent of changes in maternal magnesaemia, fetal magnesaemia showed a high degree of autonomy during both hypermagnesaemic and hy...

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Bibliographic Details
Published in:Experimental physiology 1990-09, Vol.75 (5), p.681-688
Main Authors: Barri, M, Abbas, SK, Pickard, DW, Hammonds, RG, Wood, WI, Caple, IW, Martin, TJ, Care, AD
Format: Article
Language:English
Subjects:
Animals
Female
Fetal Blood
Fetus - metabolism
Homeostasis
Ion Channels - metabolism
Magnesium - blood
Parathyroid Hormone - pharmacology
Parathyroid Hormone-Related Protein
Parathyroidectomy
Peptide Fragments - pharmacology
Perfusion
Placenta - metabolism
Pregnancy
Proteins - pharmacology
Sheep
Thyroidectomy
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Summary:The fetal plasma magnesium concentration exceeds that of the mother but the difference is small compared to that of ionized calcium concentration. Although not fully independent of changes in maternal magnesaemia, fetal magnesaemia showed a high degree of autonomy during both hypermagnesaemic and hypomagnesaemic changes induced in the ewe. As with calcium, the placental gradient is reversed after fetal thyroparathyroidectomy (TXPTX) with thyroxine replacement. During perfusion in situ of the placenta from such TXPTX fetuses isolated from the fetus itself, a stable positive placental gradient of magnesium concentration could be re-established between the perfusing blood and the maternal circulation. As with calcium, this gradient could be increased by fetal calf parathyroid extract, parathyroid hormone-related protein (PTHrP 1-141), PTHrP (1-84) but not by PTHrP (1-34). It was concluded that a mid-molecule portion of PTHrP can stimulate a putative placental pump which is responsible for the gradients of both calcium ions and magnesium across the ovine placenta.
ISSN:0958-0670
1469-445X
DOI:10.1113/expphysiol.1990.sp003446