A new method for the hydrolysis of conjugated catecholamines.

A new method of hydrolysis of conjugated CA's in plasma and urine has been developed. It is based on the lyophilization of dilute perchloric acid solutions of plasma and urine. The hydrolysis of the CA conjugates was more complete by this method than by the standard method by enzymatic hydrolysis. The identity of the products was verified by TLC. DA, undetectable in 95% of normal subjects, was found to exist almost exclusively in the conjugated form, averaging 0.74 +/- 0.17 (S.E.) ng/ml. Free and conjugated NE and E in human plasma were 0.23 +/- 0.03 and 0.32 +/- 0.27 ng/ml, respectively. The new and simple method of hydrolysis of conjugated CA's may help in the search for the physiological meaning of the conjugation.