Canine renal and systemic hemodynamic measurements after 4 weeks of a magnesium deficient diet

To probe renal hemodynamic measurements in relation to simultaneous systemic hemodynamic measurements in normal, adult, conscious dogs on a magnesium-deficient diet, 6 experimental animals were given 4 weeks of a magnesium-deficient diet compared to 9 animals whose dietary magnesium was normal. Systemic hemodynamics were estimated using a thermodilution catheter, and renal hemodynamics were estimated by standard renal clearance techniques. Electrolytes and hormones were also surveyed in these same animals at the time of hemodynamic measurements. Heart rate was significantly higher in magnesium-deficient dogs, but there were no other systemic hemodynamic differences between the two groups of dogs. Renal blood flow, effective renal plasma flow, and urinary osmolality were significantly higher in the magnesium-deficient animals. Whole-blood ionized calcium and potassium, serum magnesium, and fractional excretion of magnesium were lower in the magnesium-deficient dogs. We conclude that the renal circulation is more sensitive than the systemic circulation to disturbances in magnesium balance. Disturbances of other electrolytes accompanying magnesium deficiency were also confirmed.