Effect of water intake on Na-K-ATPase in nephron segments of the desert rodent, Jaculus orientalis.

Na-K-ATPase activity was measured in individual pieces of nephron microdissected from collagenase-treated kidneys of jerboas, Jaculus orientalis. Na-K-ATPase activity was high in the distal convoluted tubule, intermediate in the thick ascending limb of the loop of Henle and low in the proximal and collecting tubule. When jerboas were adapted for several weeks to a hydrated diet and excreted a more diluted urine, Na-K-ATPase activity was altered in specific segments of the nephron: 1. In the proximal convoluted tubule, Na-K-ATPase activity decreased, especially in the juxtamedullary nephrons, suggesting that internephron heterogeneity was diminished; 2. In the medullary thick ascending limb, but not in the cortical portion, Na-K-ATPase activity decreased by 30%; 3. Na-K-ATPase was also diminished in the cortical collecting tubules (by 20%) but not in the medullary collecting tubule. Morphometric measurements also indicate that changes in Na-K-ATPase activity observed in the thick ascending limb are correlated to a cell atrophy, whereas in the collecting tubule, they occur independently of any visible morphological alteration. These differences in Na-K-ATPase activity are likely to be secondary to the changes in the plasma concentration of vasopressin previously described during such adaptation and to be involved in the control of water and sodium handling.