Renal distribution of sodium in potassium-depleted and vitamin D-intoxicated rats

¹ Sections of Medicine, Pathologic Anatomy, and Biochemistry, Mayo Clinic and Mayo Foundation, Rochester, Minnesota

The concentration and distribution of sodium and potassium in small consecutive portions of kidneys of potassium-depleted and vitamin D-intoxicated hydropenic rats were estimated by a procedure based on the principle of specific activity. By this method sodium and potassium could be measured in bits of tissue weighing less than 2 mg. The results were correlated with the corresponding urinary osmolality. In both experimental groups, a marked impairment of the elaboration of osmotically concentrated urine was observed. The relative distribution of sodium and potassium in the kidney was not altered significantly. Associated with the decreased osmolality of the urine, however, was an approximately proportionate or slightly greater reduction in the content of sodium in the papilla. The findings suggest that a failure to establish maximal medullary hypertonicity, as indicated by the diminished accumulation of sodium, may be an important factor in the impairment of concentrating mechanisms.