<prompt> Acidification of urine occurs at:PCTLoop of HenleDCTCollecting duct  <response>: H secretion : 80-85 H secretion in the PCT 10 in the Thick ascending limb And remaining secretion occurs in the late distal tubule and collecting duct. - Although secretion in the late distal tubule and collecting duct accounts for only about 5-10 of the total H secreted, it is impoant for acidification of urine. - In PCT, H secretion can be increased only about 3-4 times, although large amounts of H is secreted by this segment. Most of it is for the re-absorption of the filtered bicarbonate. On the other hand, H concentration can be increased as much as 1000-fold in the late distal tubule and collecting duct. This decreases the pH of the tubular fluid to about 4.5. This is called the limiting pH; the maximally acidic urine is thus achieved by H secretion by this segment. 