Which of the following constitutes the hepatic reaction occuring during periods of acidosis?

When the body becomes acidotic, the liver and the kidneys play central roles in reactions designed to reduce the proton level (i.e., increase the pH) of the circulation. Which of the following constitutes the hepatic reaction occuring during periods of acidosis?

(A) ammonia incorporation into glutamateforming glutamine
(B) ammonia incorporation into alphaketoglutarate-forming glutamate
© glutamine conversion to glutamatereleasing ammonia
(D) glutamine conversion to alphaketoglutarate-releasing ammonia
(E) increased production of urea to dispose of ammonia


(A) Major reactions, that involve the regulation of plasma pH as well as the level of circulating ammonia, involve the heptatic and renal enzymes GDH, glutamine synthase (GS), and glutaminase. The liver compartmentalizes GS and glutaminase in order to control the flow of ammonia into glutamine or urea. Under acidotic conditions the liver diverts ammonia to glutamine via the GS reaction. The glutamine then enters the circulation. In fact, glutamine is the major amino acid of the circulation and its role is to ferry ammonia to and from various tissues. In the kidneys, glutamine is hydrolyzed by glutaminase (yielding glutamate) releasing the ammonia to the urine. There the ammonia ionizes to ammonium ion, NH4+, which reduces the circulating concentration of hydrogen ion resulting in an increase in the pH. Additionally, the glutamate can be converted to alphaketoglutarateyielding another mole of ammonia, which is ionized by hydrogen ions further increasing the pH. Incorporation of ammonia into alpha-ketoglutarate (choice B) would deplete the ammonia ionization reaction and lead to further acidification. Glutamine conversion to glutamate (choice C) will occur in the kidneys but not in the liver under acidotic conditions. Glutamine is not directly converted to alpha-ketoglutarate (choice D); a two-step process is required and would take place in the kidneys not in the liver under acidotic conditions as in choice C. Conversion of ammonia into urea (choice E) is the process of ridding the body of waste nitrogen, but it is not a means to regulate the pH of bodily fluids