An urine specimen is found to contain high level of ammounium ions (NH4+) is this an example of blood acidosis or alkalosis? explain
Answer: Acidosis.Explanation: Free hydrogen ions are not filtered by the kidney. Instead, they are secreted into the tubular fluid. Because free hydrogens cannot be excreted in the urine easily, there are excreted with weak acids such as H2PO4- which function as urinary buffers. Now in the presence of an increased acid load, the phosphate ions are used up and the kidney then increases its production of ammonium. That's why new bicarbonate ions are produced during ammoniagenesis. The generation of new bicarbonate ions conceptually is akin to increased hydrogen excretion. Therefore the real function of ammoniagenesis is not as an urinary buffer of hydrogen ions as is commonly inaccurately described. The real function of ammoniagensis is to increase the generation of new bicarbonate ions. Ammonium before it is excreted is first re-absorbed in the thick ascending limb, circulated in the medullary interstitium and then pumped back in the collected tubule as ammonia. In the collecting tubule, ammonia then takes up hydrogen ions secreted into the lumen by intercalated cells, to form ammonium. In order for ammoniagenesis to be effective in the generation of new HCO3-, the NH4+ produced must be excreted in the urine. NH4+ secreted in the proximal tubule is in equilibrium with a small quantity of NH3. The urine does not become maximally acidified until the collecting tubule where secretion of hydrogen ions by intercalated cells significantly reduce the urine pH. Therefore the kidney prevents loss of ammonium by reabsorbing NH4+ in the thick ascending limb and pumping it into the collecting duct where the urine pH is very low, facilitating ammonia in its protonated form. This process is enhanced during periods of acidosis when hydrogen secretion by the intercalated cells is significantly increased.