POTASSIUM PREVENTION OF LITHIUM-INDUCED LOSS OF WATER AND SODIUM IN RATS

Lithium was administered to rats with the food in amounts leading to serum lithium concentrations of 0.6-0.8 mmol/liter. The animals had free access to water and 0.46 m NaCl solution. Some of the rats were given a diet to which 500 mmol/kg of either potassium chloride or potassium phosphate had been added, while other rats received food without extra potassium. In the course of 3 weeks the water and sodium intakes increased in all groups, but they increased significantly less in the rats given potassium than in those given no extra potassium. During 6 hr of fluid deprivation the rats given extra potassium showed significantly less urine production, weight loss, and increase in serum sodium concentration. When access to NaCl solution was withdrawn the animals given extra potassium were almost unaffected whereas within 14 days the animals not given extra potassium developed lithium intoxication characterized by weight loss, decreased intake of water and food, lowered serum sodium concentration, and increased serum lithium concentration; two of the seven rats in this group died. In none of the experiments was there any difference between rats given potassium chloride and rats given potassium phosphate. The data indicate that a high potassium content in the food prevents lithium-induced renal inability to retain water and sodium. © 1979.