On the in vivo inhibition of human platelet monoamine oxidase (1.4.3.4) by pargyline

Pre- and post-partum plasma amine oxidase differences in the rhesus monkey (Macaca mulatta)

Plasma amine oxidase activity increased from 23.4 nmol/ml/h during pregnancy to 49.5 nmol/ml/h during an extended post partum period in 10 rhesus monkeys. Comparison with non-pregnant control monkeys sampled at similar times indicated that the significant differences were in the extended post partum period.

A routine assay procedure for monoamine oxidase and its application to human blood platelets

In the radiometric assay procedure for monoamine oxidase separation of the reaction products by ion-exchange column chromatography was optimized. A device was constructed that allowed the separation of 48 samples at the same time. This device can be applied for a great variety of analytical methods. With a 0.1 mM substrate concentration in the incubation mixture, reaction products could be determined with a reproducibility of 2-5%, where the standard deviation depends on the substrate. Using beta-phenylethylamine as substrate 20 mug of platelet protein was sufficient for monoamine oxidase activity determinations. The dependence of human blood platelet monoamine oxidase on age and sex were studied using the method.

Molecular biology of neurological and psychiatric disorders. I. Effect of parkinsonism, age, sex and L-dopa on platelet monoamine oxidase

Since there is substantial evidence for a nigrostriatal dopamine defect in Parkinson's disease and since monoamine oxidase (MAO) appears to be essential for the degradation of dopamine, we investigated whether this enzyme is involved in the pathogenesis of this disease or in the therapeutic action of L-dopa. To gain a solid basis for our analysis we studied some properties of platelet MAO, at present the only practical in vivo source for human MAO. Substrate and inhibitor pattern clearly pointed to a predominant B-type character of this enzyme. By using 3 substrates, m-iodobenzylamine, p-methoxybenzylamine, and tyramine, we found a marked age and sex difference in MAO activity. In untreated parkinsonian patients, platelet MAO was slightly reduced as compared with age- and sex-matched controls. Treatment with L-dopa induced a further reduction of platelet MAO activity in both sexes, but more in men than in women. We conjecture that the action of L-dopa on parkisonian patients is twofold: L-dopa is known to enhance the release of gonadotropins and thus to increase the production of sex hormones which in turn are capable of reducing MAO activity. Dopamine, formed from L-dopa, may thus have a better chance for survival in reaching the dopaminergic receptor. A new form of therapy, based on this concept, is proposed.