A kinetic determination of ammonia in plasma

Abstract

A simple and rapid method is described for the determination of ammonia in plasma without deproteinization, using the enzyme glutamate dehydrogenase and NADPH as coenzyme. ADP is used to stabilize glutamate dehydrogenase.

The measuring principle is a kinetic one, determining the reaction rate on the “Enzyrator”. The whole determination takes only 7 min, including the preincubation time.

The plasma sample is only 100 μl, which makes it possible to determine the ammonia values in capillary blood. Comparing the values of venous and capillary blood, we found that capillary values are 2–3 times higher than those in venous blood.

The normal range for venous plasma NHs was 6.5–35.0 μmol/l. The mean value of non-fasting persons was 22.0 μmol/l.