Tissue electrolyte changes induced by high doses of diuretics in rats

High doses of furosemide administered orally to growing rats for 4 weeks induced a pronounced fall in the concentration of magnesium and potassium in plasma, of magnesium in bone and potassium in skeletal muscle, but did not cause any reduction of these ions in the myocardium. The only electrolyte change in the heart of furosemide exposed rats was a higher calcium concentration than in rats of the control group. The addition of amiloride to furosemide in the ratio 1:16 mg corrected and partly overcorrected for the losses of magnesium and potassium in plasma and skeletal muscle. It is concluded that long term amiloride administration prevented magnesium and potassium losses induced by furosemide and that the myocardium was relatively resistant to furosemide induced magnesium and potassium loss.