INTENDED USE
For the quantitative in vitro determination of Ammonia in plasma.
PRINCIPLE OF THE METHOD(1, 4, 5)
Ammonia combines with α-ketoglutarate and NADPH in the presence of
glutamate dehydrogenase (GLDH) to yield glutamate and NADP+. The
corresponding decrease in absorbance at 340 nm is proportional to the
plasma ammonia concentration.
GLDH
α-ketoglutarate + NH3+NADPH glutamate+ NADP+
CLINICAL SIGNIFICANCE
The major source of circulating ammonia is the GI tract. Under normal
conditions, ammonia is metabolized to urea by liver enzymes. Several
diseases, both inherited and acquired, cause elevated ammonia
(hyperammonemia). The inherited deficiencies of urea cycle enzymes are
the major cause of hyperammonemia in infants. The acquired
hyperammonemia diseases are caused by liver disease, renal failure, and
Reye’s syndrome. Elevated ammonia is toxic to the central nervous system.
STORAGE AND STABILITY
R1 (reagent reconstituted with buffer) is stable 5 days at 15-25 ºC or 3 weeks
at 2-8 ºC,stored in the absence of bacterial contamination. The other
components of the kit are stable until the expiration date on the label when
stored tightly closed at 2-8ºC, protected from light and contaminations
prevented during their use. Do not use reagents over the expiration date.
ADDITIONAL EQUIPMENT
- Spectrophotometer or colorimeter measuring at 340 nm.
- Thermostatic bath at 37º C ( 0,1ºC)
- Matched cuvettes 1,0 cm light path.
- General laboratory equipment (Note 1).
SAMPLES (2)
Heparinized plasma or EDTA plasma.
Blood is collected from a stasis-free vein and stored in an ice bath. The
plasma is then separated within 30 min. Ammonia assay should be carried
out immediately. The plasma may be stored for 2 hours at 2-8 C.
INTERFERENCES(3)
Haemolysis interferes with the assay.
NOTES
1. In order to avoid contamination it is recommended to use disposable material.
2. SPINREACT has instruction sheets for several automatic analyzers.
Instructions for many of them are available on request.
