ROLE OF DIETARY MAGNESIUM-DEFICIENCY IN THE PRESSER AND ARRHYTHMOGENIC RESPONSE TO EPINEPHRINE IN THE INTACT DOG

The effect of dietary magnesium deficiency on the presser and arrhythm ogenic responses to epinephrine was investigated in 19 dogs maintained either on a normal diet (11 dogs) or a diet deficient in magnesium (8 dogs). Magnesium-deficient dogs had significantly lower serum magnesi um levels than the control dogs on a normal diet. Magnesium-deficient dogs showed an increased presser sensitivity to epinephrine as determi ned by the dose of epinephrine required to cause a maximal presser res ponse (3.4 mu g/kg/min compared to 13.4 mu g/kg/min, p < 0.05). Magnes ium-deficient dogs also had a significantly lower threshold dose for v entricular premature beats (0.8 mu g/kg/min compared to 2.7 mu g/kg/mi n, p < 0.05). Acute administration of magnesium sulfate restored press er sensitivity and ventricular premature beat threshold to normal leve ls in the magnesium-deficient dogs. Threshold dose for ventricular tac hycardia beat was similar in both normal and magnesium-deficient dogs, and threshold was raised significantly in both groups by acute admini stration of magnesium.