Pharmacological characterization of lithium reabsorption in the rat

The effects of furosemide, chlorothiazide and acetazolamide upon fractional lithium excretion (FELi) were studied in acutely lithium-loaded rats. Changes in FELi were compared with the fractional excretions of sodium FENa and calcium FECa. Furosemide and acetazolamide, given separately, produced large and substantially equivalent increases in FELi. Responses of FENa and FECa to acetazolamide were much less than to furosemide. Chlorothiazide, alone or in combination with the other agents, produced moderate increases in FENa, modest increases in FECa and essentially no change in FELi. When furosemide was superimposed upon a previously established acetazolamide diuresis, the response in FELi was additive to that from acetazolamide alone. These results suggest that lithium reabsorption occurs at nephron sites primarily affected by acetazolamide and furosemide in the rat and that a significant amount of lithium reabsorption may take place in the loop of Henle. Acetazolamide, in combination with furosemide, appeared to depress renal tissue lithium accumulation.