Ammonia urinary excretion

Glycine can be reduced to acetate and ammonia by the selenium-dependent clostridial glycine reductase system (Eq. 15-61). A variety of additional products can be formed from glycine as is indicated in Fig. 24-20. Hippuiic acid (Box 10-A), the usual urinary excretion product in the "detoxication" of benzoic acid, is formed via benzoyl-CoA (Eq. 24-43) ... 

When absorbed into the systemic circulation, ammonia is primarily excreted by the kidney as urea and urinary ammonium compounds (Gay et al. 1969 Pitts 1971). Absorbed ammonia also can be excreted as urea in feces (Richards et al. 1975) and as a perspiration constituent (Guyton 1981 Wands 1981). In a study of male subjects exposed to ammonia at concentrations up to 500 ppm for 30 min, Silverman et al. (1949) found that 70-80% of inhaled ammonia was excreted in expired air. Ammonia in expired air returned to normal concentrations within 3 to 8 min after exposure was stopped. The investigators calculated that if all the retained ammonia were absorbed into the blood, there would be no significant change in blood or urine urea, ammonia, or nonprotein nitrogen. 

With the onset of starvation, aldosterone secretion increases with the results of increased urinary excretion and decreased plasma concentration of potassium. Magnesium, calcium, and phosphate are affected similarly, although the urinary excretion of phosphate gradually declines. The absolute urinary excretion of ammonia and creatinine increases with prolonged starvation but that of urea decreases. 

On a low protein diet, when the blood ammonia is considerably decreased, the urinary excretion of these compounds is also reduced. Even so some orotic acid and uracil is always found, although uridine may be completely absent from the urine (L6). 

The kidney plays a major role in the maintenance of acid-base homeostasis, particiilarly with respect to metabolic acidosis. In response to metabolic acidosis, the kidney is able to increase its production of ammonia resulting in enhanced urinary ammonium excretion, a process linked to proton excretion and the generation of... 

If possible, the kidneys respond to restore the normal pH by increased excretion of acid and preservation of base (increased rate of Na -H exchange, increased ammonia formation, and increased reabsorption of bicarbonate). When the renal compensating mechanisms are ftinction-ing, urinary acidity and urinary ammonia are increased. The total amount of excreted may be as much as... 

In patients with adequate renal function, urinary pH values are usually increased because of the decreased excretion of acid and increased excretion of bicarbonate. Urinary ammonia values are decreased because of decreased formation of ammonia in the tubules. In K depletion, is preferentially exchanged for Na and the pH of the urine may be low. This is called paradoxical aciduria. 

Nitrogen is eliminated from the body as urea and ammonia. Urea synthesized in the liver is excreted by the kidneys. Urinary ammonia is produced in the kidney. The nitrogen in other tissues is transported to the liver and kidney in... 

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