Renal Tubular Acidosis Type IV

[coreytayloris]

Hi lads,
can anyone help explain the below to me.

specifically I don't understand

"the alkalotic environment in the renal tubular cells inhibits ammonia and hydrogen production and secretion, reducing the kidney's ability to excrete the generated acid. low ammonia levels decrease the buffering capacity of the urine for generated iron."

Also, what has aldosterone got to do with ammonia ??

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[Mcat35]

The main thing u need to know about RTA IV it is the only RTA with hyperkalemia caused by hypoaldosteronism or a mechanism that affects the Ald receptor. This would lead to Hyperkalemia because of the effect of Ald on Na+/K+ exchanger on basolateral side of cells of the collecting duct. When this occurs, this also causes less H+ secretion by the alpha - intercalated cells of the collecting duct. This cell has 2 transporters, a H+ ATPase and a H+/K+ ATPase both aid in secretion of H+ into the lumen. The H+ ATPase is also stimulated by aldosterone. When H+ is secreted into tubular fluid, NH3 (from the metabolization of glutamine) diffuses from its high concentration in the medullary interstitial fluid into the lumen of the collecting duct. Where it combines with the secreted H+ to form NH4+. When there is a lack of H+ in the lumen because of Hyperkalemia and the lack of Aldosterone effect on H+ ATPase, NH3 is not needed. Therefore its production would be limited.

 

[coreytayloris]

thank you.