netter120

ienal Produclion of New HCO,

RENAL PHYSIOLOGY

NH4A - acid

Net Acid txcretion(NAE)«(U_uxV) - (U_NH4*V) + (U_H<0 xV)

|. Perkins

MS, MFA ■■KON

Figurę 6.18 Renal Production of Nfw HCO]^- —

The kidneys generate new HCO,* lo repłenish that which is lost during the titration of the daily acid load. This occurs by the process of net acid excretk>n (NAD. Normally, the entire filtered load Ol HCOj" is reabsorbed (see Figurę 6.17), and nono appears in the unne. Tłiis process doos not produce new HCO;, bul sirnpfy prevents its los$ rrom the body. New HCO," is produced when the kidneys excrete H' with urinary buffers (the pnmary urino buffer is phosphate.ł and when rhe kidneys produce and excrete MM,'. The production and excretion ot NH/ is the most important component of NAF because these

processes are reguła lei) in rusppnse lo acid-base disorders. Acidosis stimulatos NH,' production (from glulaminein the pr«ximal lubulei and its excretion, whereas alkalosis inhibits these process. Acid-base balance is maintained when NAE is iho same as the daily acid load. which is approximately 1 mFq/kg body weighł/day. Abtncvi^lions. L'_IV Urine concenlration ol lilratable acid; urine concentration of ammonium; U,_KOy urine conc entration of biiarbonate; V ~ urine flow ratę.

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