INFLUENCE OF TEMPERATURE AND SHORT-TERM STORAGE ON THE STABILITY OF NOREPINEPHRINE IN PLASMA SAMPLES

Catecholamines, as endogenous substances, are subject to biological de gradation. The conditions of plasma handling for the determination of norepinephrine were investigated by using plasma samples of patients a nd control subjects with special regard to temperature and duration of storage. Previous studies have reported a remarkable i.v. stability o f plasma norepinephrine for several hours. Here these findings were su pported in a series of plasma samples which were kept either at 0-degr ee-C or at room temperature. Another series of samples, which had been frozen immediately after collection, stored and rethawed, showed, how ever, great losses in norepinephrine within 1 to 2 h upon standing. Th is degradation of norepinephrine could not be attributed to monoamine oxidase (MAO) activity, because the addition of the MAO inhibitor parg yline was found to have no influence on the stability of norepinephrin e. Recommendations for handling and storing of plasma samples for nore pinephrine determinations are given.