Measured Ammonia Concentrations Research Articles

Application of the Phenol—Hypochlorite Reaction to Measurement of Ammonia Concentrations in Kjeldahl Digests of Serum and Various Tissues

Abstract Conditions have been defined that enable the use of nitroprusside as a catalyst for the phenol-hypochlorite reaction when the latter is applied to measurement of nitrogen in Kjeldahl digests containing mercury. This is accomplished by lowering the concentration of mercury to a range where it remains effective in accelerating the destruction of organic matter during digestion but no longer reacts with nitroprusside. In addition, the use of minimal concentrations of nitroprusside diminishes further the possibility of interference by mercury and has the added advantage of decreasing the pH dependence of indophenol blue formation. The sensitivity of the reaction makes possible measurement of nitrogen in very small samples with relatively short digestion times.

CONTRIBUTION OF THE PROXIMAL TUBULE TO URINARY AMMONIA EXCRETION BY THE DOG.

Measurements of ammonia concentration were performed on 48 samples of proximal tubular fluid from antidiuretic dogs during normal acid-base balance, and acute or chronic ammonium chloride acidosis. Measurable concentrations of ammonia (>0.3 mmoles/liter) were not detectable in proximal fluid during either normal acid-base balance or acute ammonium chloride acidosis. However, in both conditions, an ammonia concentration in proximal fluid of less than 0.3 mmoles/liter could still have accounted for a large percentage of urinary ammonia. For this reason, the present data can neither confirm nor deny the existence of ammonia addition to proximal tubular fluid during normal acid-base balance and acute metabolic acidosis. In contrast, chronic metabolic acidosis was accompanied by the definite appearance of ammonia in proximal fluid, its concentration averaging 0.82 ± .32 mmoles/liter. This observation demonstrates clearly that net ammonia addition can be observed along the proximal tubule under certain circumstances. It suggests further that the proximal tubule also contributes to the adaptive rise of urinary ammonia excretion during chronic acidosis.