Protection by magnesium of renal calcinosis in furosemide-treated weanling rats with moderate magnesium deficiency.

Prolonged treatment of premature infants with the potent diuretic furosemide has resulted in hypercalciuria, sometimes with renal calcinosis and other complications. Furosemide was administered to weanling rats to explore its effect on magnesium and calcium metabolism. The animals were fed purified diets providing 40 mg magnesium/100 g diet or 10 mg magnesium/100 g. Half of each dietary group (40-F or 10-F) received 18 doses of furosemide, 20 mg/kg body weight, intraperitoneally between days 7 and 35, and half received normal saline intraperitoneally (40-O or 10-O). Furosemide had little effect on the magnesium-sufficient animals (40-F), but comparison of 10-O and 10-F data showed that it aggravated the magnesium-deficiency syndrome. Comparison of data from 40-F and 10-F animals showed the protective effect of magnesium in preserving calcium homeostasis in furosemide-treated animals: the elevation of calcium values in 10-F rats was greater in plasma (p less than 0.0005), heart (p less than 0.0025), and kidney (p less than 0.0005). Stated another way, furosemide was associated with severely disordered calcium metabolism only in animals fed suboptimal magnesium. Studies exploring the role of magnesium in furosemide-treated infants can be recommended.