title: Infusion of Mg in humans acutely reduces serum insulin levels: a pilot study.
abstract: BACKGROUND
  Infusion of Mg for therapeutic purposes is still a matter for debate. Dosages vary considerably, yet subclinical effects on normal physiology are largely ignored. In human and animal models, interactions between Mg and insulin exist, thus we have investigated the effect of infusing Mg on serum insulin, ionised Mg (Mg(2+)) and Ca (Ca(2+)) and plasma glucose in human volunteers.
  
  
  METHODS
  Six male volunteers were infused with magnesium sulphate (MgSO(4)) dissolved in normal saline, using a high-dose "loading" bolus, followed by a lower-level "maintenance" period.
  
  
  RESULTS
  Serum Mg(2+) rose rapidly throughout the bolus infusion, declined during the maintenance phase, but remained higher than pre-infusion levels throughout the experimental period; serum Ca(2+) rose when serum Mg(2+) was highest. Infusion of MgSO(4) had no effect on heart rate or blood pressure, but caused a rapid, pronounced drop in circulating fasting insulin (p<0.0005), which slowly recovered to basal values during the course of the maintenance infusion. A slight, transient rise in plasma glucose (p<0.05) concomitant with the decline in serum insulin was also observed.
  
  
  CONCLUSIONS
  It is possible that the effect of Mg(2+) on insulin may have been due to antagonism of Ca(2+) entry in pancreatic beta-cells, the insulin decline causing a subsequent rise in circulating glucose levels. We suggest that these effects of MgSO(4) infusions should be considered where the aim is to achieve high doses of blood Mg(2+) levels by clinical intervention.
authors: Dietetics, Nutrition, and Biological Sciences, Queen Margaret University, Queen Margaret University Drive, Musselburgh, EH21 6UU. igow@qmu.ac.uk
authors: Iain F
authors: IF
authors: Gow
authors: Maureen
authors: M
authors: O'Donnell
authors: Laura
authors: L
authors: Flint
authors: Andrew D
authors: AD
authors: Flapan
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000097:blood; D015536:Down-Regulation / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007260:Infusion Pumps; D007328:Insulin / Q000097:blood*; D008274:Magnesium / Q000008:administration & dosage*; D008278:Magnesium Sulfate / Q000008:administration & dosage; D008297:Male; D010865:Pilot Projects; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D007328:Insulin; D008278:Magnesium Sulfate; D008274:Magnesium; D002118:Calcium