Effect of magnesium infusion on calcium handling in the rat kidney

Anaesthesized rats were infused with 100 microliters min-1 of 0.9% saline or saline containing 2 or 4 mmol l-1 of magnesium chloride and renal function was studied. Magnesium had no effect on urine flow rate, excretion of sodium or potassium, or glomerular filtration rate (GFR). Infusion of either dose of magnesium increased calcium excretion and calcium concentration in the urine. The increased urinary calcium excretion is due to a decrease in tubular reabsorption of calcium.