Renal response to potassium infusion in rats given lithium for prolonged time

The effects of infusion of potassium chloride was studied in Wistar rats given lithium by the food for more than 3 weeks. The animals were anaesthetized with amytal and three clearance periods were run. During periods 1 and 3 0.15 M NcCl was infused at a rate of 0.02 ml/min. for 60 min. and in period 2 0.5 M KCl was infused at the same rate for 90 min. Potassium infusion led to an increase of potassium excretion. Sodium excretion and urine flow were positive linear correlated to the potassium excretion but in rats given lithium the effect of potassium on sodium excretion was about eight times higher and the effect on urine flow about thirteen times higher than the effects on control rats not given lithium. The concentration of Na and K in the urine of the lithium-treated group were within a narrow range and almost unaffected by potassium infusion. Lithium clearance and the fractional excretion of lithium rose significantly during potassium infusion. Inulin clearance was almost unaffected by the potassium infusion. The results indicate that potassium infusion in rats given lithium for prolonged time leads to an increase of renal sodium, water and lithium excretion.