Effect of diet on distribution of urea and electrolytes in kidneys of sheep

¹ Department of Zoology, Duke University, Durham, North Carolina

In sheep and other mammals on normal protein intake, the kidney urea concentration showed an increase from cortex to papilla, and the urine urea concentration was usually higher than in the tissue. In sheep on low-protein diet, the highest urea concentration was found in the inner stripe of the outer zone of the medulla, where it was 5–15 times the urine urea concentration. At the tip of the papilla, it was only slightly higher than in the urine. The electrolyte distribution in kidneys of sheep on normal and low protein diet differed in one important respect. In normal protein sheep, the electrolyte concentration in the papilla was usually higher than in the urine. In contrast, in low protein sheep, it was lower in all zones of the kidney than in the urine. However, because of the accumulated urea in the outer zone of the medulla, the osmotic concentration in this zone equaled the osmotic concentration of the urine.

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