S-Mg does not change inversely to S-FFA during acute stress situations

The apparently divergent changes in serum magnesium (S-Mg) and serum free fatty acids (S-FFA) in stress situations associated with elevated levels of circulating adrenaline were studied experimentally in 12 healthy volunteers, who were each given three adrenaline infusions (0.05 micrograms/kg bw/min over one hundred twenty minutes). Before the adrenaline infusions the volunteers were treated for three days with either a non-selective beta-blocking agent (propranolol) or a beta-1-selective agent (atenolol) or with placebo. Six of the volunteers underwent a fourth adrenaline infusion after pretreatment with a beta-2-selective beta-blocking agent (ICI 118551). S-Mg and S-FFA were determined every fifteen minutes. After pretreatment with placebo, adrenaline infusion caused an increase in S-FFA from 0.22 +/- 0.20 mmol/L (mean +/- SD) to max 0.59 +/- 0.39 mmol/L after thirty minutes of adrenaline infusion (p less than 0.001). At one hundred twenty minutes S-FFA had decreased to 0.35 +/- 0.26 mmol/L. Thirty minutes after cessation of the adrenaline infusion, S-FFA had returned to the same level as before the infusion. S-Mg before the adrenaline infusion was 0.83 +/- 0.05 mmol/L, rose to 0.85 +/- 0.05 at fifteen minutes, and then decreased to 0.78 +/- 0.05 at one hundred thirty-five minutes (p less than 0.05). Pretreatment with atenolol did not change this pattern, although the changes in S-FFA and S-Mg were of a smaller magnitude but still statistically significant.