Demographic, biologic, and other variables affecting monoamine oxidase activity.

Monoamine oxidase (MAO) activity has been shown to be influenced by a variety of demographic, biologic, and other variables. Human platelet, plasma, and brain enzyme activities correlate with age and are higher in women. Brain catecholamines tend to decrease with age. The acute effects of ethanol on platelet MAO do not appear to be significant, but chronic ethanol ingestion could influence enzyme activity through a variety of possible mechanisms. Numerous drugs and hormones have been shown to alter platelet and tissue MAO. Heterogeneity of platelet size, density, age, and enzyme activity complicates the study of MAO in clinical populations. Newer platelet isolation techniques may diminish the variability due to platelet sampling. Studies of platelet MAO activity in schizophrenia require that careful attention be given to controlling for variables possibly influencing the blood enzyme activity, such as prior neuroleptic treatment. The limited studies of brain MAO activity in man fail to demonstrate differences between patients with schizophrenia and normal controls.