Radioenzymatic assay of plasma adrenaline and noradrenaline: evidence for a catechol-O-methyltransferase (COMT) inhibiting factor associated with essential hypertension.

During the evaluation of a modified radioenzymatic determination of plasma adrenaline and noradrenaline, it has been found that there exists a highly significant (p less than 0.001) negative correlation between the amount of radioactivity incorporated in the internal standard added to plasma and the period during which the plasma had been stored at -25 degrees C, but only in plasma from patients with essential hypertension. Plasma from normotensive persons exhibits a complete lack of correlation between these factors. The consequences of the hypertension-associated COMT-inhibiting factor for the assays' specifications are discussed and data are presented for comparison with a recently described uremia-associated COMT-inhibitor (Demassieux et al, Clin Chim Acta 115, 377--391; 1981).