Electrolyte, water, and urea content in dog kidneys in different states of diuresis.

Abstract

Thin kidney slices of dogs in hydropenia and water diuresis were analyzed for water, electrolytes, and urea content. The sodium and chloride contents are uniform throughout the cortex, but rise very markedly in the outer medulla, more during hydropenia than during water diuresis. Throughout the inner medulla a uniform content was observed, about 30% higher during hydropenia. The water content was uniform at all levels in the cortex, and increasing in the outer medulla, regardless of the state of hydration. In the inner medulla the content rose toward the papilla during water diuresis and decreased in the same direction during hydropenia. The urea content showed a very marked rise throughout the medulla during hydropenia and no significant rise during water diuresis. It was concluded that the great bulk of medullary sodium is pumped in the thick portion of the ascending limb of Henle and that the changes in water and urea contents bear the main responsibility in the creation of osmotic gradients within the inner medulla during hydropenia.