Effects of ureteral ligation on renal medullary lesions of potassium depletion

In diet-induced potassium depleted rats, tissue potassium content of the renal medulla decreases and membrane-bound droplets form in the cytoplasm of medullary cells. To elucidate the interrelationship between medullary potassium concentration and intracytoplasmic droplets, ligation of the left ureter was performed on rats deprived of potassium for 2 weeks. Our results show that, even in the absence of supplemental potassium provision to the animal, a unilateral rise in tissue potassium of the ligated left kidney was significant. After 4 days of ligation, the left medullary potassium was 41.96 +/- 0.79 mEq/100 g dry weight compared to 32.51 +/- 0.84 mEq/100 g dry weight (P less than 0.001) of medullary potassium in the non-ligated right kidney. The rise in tissue potassium in the left kidney coincided with the dissolution of intracytoplasmic droplets. We conclude, that mechanical obstruction to urinary flow can dissolve storage droplets in medullary cells and that the lysis of droplets is made possible by the increase in medullary tissue potassium content.