Monoamine oxidase inhibitors and whole blood, platelet and plasma monoamine oxidase.

1. Whole lysed blood monoamine oxidase activity using benzylamine as substrate, represents an addition of platelet and plasma activity. 2. Enzyme activity measured in whole lysed blood in the presence of 10(-4)M pargyline gave a value equivalent to plasma monoamine oxidase, and by subtraction gives a value for platelet enzyme activity. 3. This method of measuring platelet and plasma monoamine oxidase activities from a single whole blood sample, has the advantage of not requiring physical separation of the blood fraction.