Effect of Magnesium Sulfate Concentration on Serum Ionized Magnesium In Vitro

ABSTRACT

We undertook this in vitro study to quantify the effect that addition of magnesium (Mg) sulfate to neonatal serum, as compared with adult serum, might have on ionized Mg (Mg²⁺) concentration. We used one cord blood sample and one adult blood sample that we made hypermagnesemic by adding various amounts of magnesium sulfate to study five levels of serum Mg. Each sample was then studied at one of three levels of pH, from extreme alkalosis to extreme acidosis. We measured the changes in serum Mg²⁺ and serum ionized calcium (Ca²⁺) in reaction to these changes in pH and Mg. At each pH level, there was an exponential increase in the serum Mg²⁺ (and no significant change in serum Ca²⁺) with increasing serum Mg. Multiple regression analysis using Mg²⁺ as the dependent variable and baseline Ca²⁺, phosphorous, albumin, and blood type (adult versus cord blood) as well as blood pH and serum Mg as independent variables indicated that serum Mg and pH were the only variables significantly influencing serum Mg²⁺. Within the range of serum Mg considered, the addition of magnesium sulfate in vitro causes an exponential increase in Mg²⁺ and no significant change in serum Ca²⁺.

KEYWORDS

Magnesium supplementation - ionized magnesium

REFERENCES

• 1 Mimouni F, Tsang R C. Perinatal magnesium metabolism: personal data and challenges for the 1990s.  Magnes Res. 1991;  4 109-117
• 2 Elliott J P. Magnesium sulfate as a tocolytic agent.  Am J Obstet Gynecol. 1983;  147 277-284
• 3 Liu T L. Preliminary report on the treatment of severe preeclampsia-eclampsia with magnesium sulfate and volume expanders.  Am J Obstet Gynecol. 1982;  144 983-984
• 4 Miller R K, Berndt W O. Evidence for Mg 2 + -dependent, Na +  + K + -activated ATPase and Ca 2 + -ATPase in the human term placenta.  Proc Soc Exp Biol Med. 1973;  143 118-122
• 5 Mimouni F, Mughal Z, Hammond G. Placental calcium transport during acute maternal hypermagnesemia in the rat.  Am J Obstet Gynecol. 1993;  168(3 Pt 1) 984-987
• 6 Rasch D K, Huber P A, Richardson C J, L’Hommedieu C S, Nelson T E, Reddi R. Neurobehavioral effects of neonatal hypermagnesemia.  J Pediatr. 1982;  100 272-276
• 7 Mimouni F B. The ion-selective magnesium electrode: a new tool for clinicians and investigators.  J Am Coll Nutr. 1996;  15 4-5
• 8 Lockitch G, Halstead A C, Albersheim S, MacCallum C, Quigley G. Age- and sex-specific pediatric reference intervals for biochemistry analytes as measured with the Ektachem-700 analyzer.  Clin Chem. 1988;  34 1622-1625
• 9 http://en.wikipedia.org/wiki/Law_of_mass_action Accessed 11/10/2009
• 10 Frisch L S, Mimouni F. Hypomagnesemia following correction of metabolic acidosis: a case of hungry bones.  J Am Coll Nutr. 1993;  12 710-713
• 11 Navarro J F, Macía M L, Gallego E et al.. Serum magnesium concentration and PTH levels. Is long-term chronic hypermagnesemia a risk factor for adynamic bone disease?.  Scand J Urol Nephrol. 1997;  31 275-280
• 12 Halhali A, Wimalawansa S J, Berentsen V, Avila E, Thota C S, Larrea F. Calcitonin gene- and parathyroid hormone-related peptides in preeclampsia: effects of magnesium sulfate.  Obstet Gynecol. 2001;  97 893-897
• 13 Dincsoy M Y, Tsang R C, Laskarzewski P, Ho M, Chen I W, Davis N. Serum calcitonin response to administration of calcium in newborn infants during exchange blood transfusion.  J Pediatr. 1982;  100 782-786
• 14 Dincsoy M Y, Tsang R C, Laskarzewski P et al.. The role of postnatal age and magnesium on parathyroid hormone responses during “exchange” blood transfusion in the newborn period.  J Pediatr. 1982;  100 277-283
• 15 Mimouni F, Loughead J L, Tsang R C, Khoury J. Postnatal surge in serum calcitonin concentrations: no contribution to neonatal hypocalcemia in infants of diabetic mothers.  Pediatr Res. 1990;  28 493-495
• 16 Dollberg S, Kupietz M, Mimouni F B. Effect of albumin on neonatal serum ionized magnesium in vitro.  Magnes Res. 2002;  15 237-240