Investigation into intraerythrocytic and extraerythrocytic acid-base and electrolyte changes after long-term ammonium chloride administration in dogs.

OBJECTIVES

To investigate the effect of ammonium chloride-induced urine acidification on acid-base status (ABS) of blood, plasma, and erythrocytes, and to compare the diagnostic value of acid-base analysis for erythrocytes with that for blood and plasma.

DESIGN

Ammonium chloride (100 mg/kg of body weight) was administered orally every 12 hours for 8 consecutive days. The ABS was determined daily in venous blood, plasma, and lysed, packed erythrocytes (erythrolysate) and in urine. In plasma and erythrocytes, concentrations of sodium Na+) and potassium (K+) were analyzed.

ANIMALS

16 clinically normal (8 treated and 8 control dogs.

PROCEDURE

The acid-base analysis (standard pH, standard bicarbonate concentration, base excess, and carbon dioxide tension) in blood, plasma, and erythrocytes was determined by use of the CO2, O2 gas equilibration method. Determination of urine ABS (pH, concentrations of acids and bases, net acid-base excretion, base-acid quotient) was performed by titration methods. Determination of concentrations of Na+ and K+ in erythrocytes was performed by flame photometry, and in plasma, by use of ion-specific electrodes.

RESULTS

Ammonium chloride caused metabolic acidosis in blood and plasma, but no change of ABS in erythrocytes. The concentrations of K+ in plasma and erythrocytes did not change in treated dogs; however, the concentrations of Na+ in plasma and erythrocytes decreased significantly (P < 0.05) after ammonium chloride administration. Urinary acid excretion increased significantly (P < 0.05) in treated dogs; urine pH was between 4.51 and 5.49 at all times.

CONCLUSIONS

Ammonium chloride administration (100 mg/kg, PO, q 12 h) causes substantial blood and urine acidification but does not influence erythrocyte ABS. In this study, determination of erythrocyte ABS did not provide any additional benefit in diagnosing metabolic acidosis, compared with analysis of blood.