The high osmolarity of the renal medulla is maintained by all the following, except  

The high osmolarity of the renal medulla is maintained by the secretion of urea from the thin segment of the ascending limb of Henle's loop. Urea contributes to the concentration gradient in the medulla, which is essential for the reabsorption of water in the collecting ducts. This mechanism plays a crucial role in the kidney's ability to regulate water balance and concentrate urine.