CATECHOL-O-METHYLTRANSFERASE .I. AN ENZYMATIC ASSAY FOR CARDIAC NOREPINEPHRINE

Nanogram quantities of norepinephrine from heart tissue were assayed enzymatically by using purified catechol-O-methyltransferase and S-adenosylmethio-nine-methyI-14C. Conditions for extraction of tissues and incubations were optimized. The product of the enzymatic reaction, normetanephrine-methyl-14C, was extracted and measured by scintillation spectrometry. Cardiac norepinephrine levels were measured by this method in rat and guinea pig, and also in mouse, both before and after treatment with drugs that alter levels of norepinephrine. The results were in agreement with those obtained by the standard fluorometric assay for norepinephrine. It is suggested that, in combination with thin-layer separation of the O-methylated products, the method may be used for the simultaneous assay of dopamine, norepinephrine and epinephrine. © 1969.