ABSTRACT
Monoamine oxidase (MAO; EC 1.4.3.4.) was measured in whole blood with kynuramine as the substrate. Optimal circumstances were determined. By use of selective inhibitors, gradient centrifugation, dilution of samples and removal of thrombocytes from whole blood it was shown that this assay of MAO in whole blood is in fact a determination of platelet MAO. No reversible endogenous inhibitors are present in the blood. Because preparation of platelet-rich plasma may lead to considerable losses of specific subpopulations with relatively low or high enzyme activities, the advantage of using whole blood is that the MAO activity is determined in the whole platelet population.
Subject(s)
Blood Platelets/enzymology , Monoamine Oxidase/blood , Centrifugation, Density Gradient , Humans , Kynuramine , Monoamine Oxidase Inhibitors/blood , Monoamine Oxidase Inhibitors/pharmacologyABSTRACT
Washing of erythrocytes from healthy volunteers in an isotonic sodium chloride solution at pH 5.6 results in the occurrence of plasma membrane elevations as observed in freeze-etch electron microscopy. This is prevented by anion permeability inhibiting agents. In the absence of these agents a reduced number of elevations was found in 23 of 36 patients with a major depressive episode. This reduced capacity to form membrane elevations was positively correlated with a genetic vulnerability, defined as an admission to a psychiatric hospital in first-degree relatives.
