1. The effect of acute potassium infusion on renal tubular reabsorption of potassium by magnesium-deficient and pair-fed control rats has been studied by the recollection micropuncture method.
2. During potassium chloride infusion, the amount of potassium remaining in the distal tubule is lower in magnesium-deficient than in pair-fed rats. This could be due to a reduction in potassium secretion or to an enhancement of potassium reabsorption.
3. The present study demonstrates enhanced renal potassium retention in the magnesium-deficient rat, and is in contrast to previous reports of renal potassium wasting in this circumstance.