Mention the substances that exit from the tubules in order to maintain a concentration gradient in the medullary interstitium.

(N/A) The substances that exit from the renal tubules to maintain the concentration gradient in the medullary interstitium are $NaCl$,$H_{2}O$,and urea.
$NaCl$ is transported by the ascending limb of the loop of Henle.
$H_{2}O$ is removed from the descending limb of the loop of Henle and the collecting duct.
Urea is transported out of the collecting duct into the medullary interstitium to contribute to the high osmolarity.