Alterations in the Countercurrent Gradient by Lesions in the Median Eminence

IT is well established that hypertonic urine is produced in. the kidney by means of a countercurrent multiplier system and that the formation of such urine requires a hyper-osmotic medullary interstitium. It is accepted that anti-diuretic hormone regulates the osmolality of the urine so produced by altering the permeability characteristics of" the distal areas of the nephron.