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PubMed1997

Age and sex related alterations in serum and platelet monoamine oxidase.

The process of aging presents itself with various alterations in physiological events. Although the turnover of catecholamines increases with aging, there is a lack of response to catecholamines in target tissues. One of the key enzymes in catecholamine metabolism is monoamine oxidase. It has been suggested that tissue and serum monoamine oxidase activities show pathological alterations in various diseases while physiological fluctuations can also be detected in normals. The aim of this study is to determine the sex and age related changes of platelet and serum monoamine oxidase in healthy volunteers. In this study, 75 healthy volunteers of different ages (21-80 a) and sexes (40 females, 35 males) were included. Serum and platelet monoamine oxidase determinations were performed spectrophotofluorometrically by Tufvesson's (Scand J Clin Lab Invest 1970; 26:151-4) and Kraml's (Biochem Pharmacol 1965; 14:1684-6) modified methods, respectively. While there was no significant difference in serum monoamine oxidase activities related to age and sex, platelet monoamine oxidase manifested a significant increase in females compared to males (p < 0.05) and the mean values in both sexes showed an increase with age (p < 0.001). The results of this study imply that platelet monoamine oxidase shows an age related increase which is more prominent in females.

Adult↗

PubMed1979

A correlation between platelet monoamine oxidase activity and plasma prolactin concentrations in man.

Increases in plasma prolactin concentrations produced by alpha-methyl-p-tyrosine, a catecholamine synthesis inhibitor, varied inversely with baseline platelet monoamine oxidase activity in 12 patients with chronic schizophrenia. In normal volunteers with low monoamine oxidase activity and in unmedicated patients with chronic schizophrenia, plasma prolactin concentrations varied directly with platelet monoamine oxidase activity. No such relationship was found in normal subjects with high platelet monoamine oxidase activity. These data suggest that platelet monoamine oxidase activity reflects monoaminergic activity in the tubero-infundibular system, which in turn affects plasma prolactin concentrations. This relationship may be important in patients with low platelet monoamine oxidase activity, such as some chronic schizophrenics.

Blood Platelets↗

PubMed1989

Metabolism of monoamine oxidase inhibitors.

1. Despite the fact that monoamine oxidase inhibitors have been used clinically and in animal experiments for many years, much still remains unknown about their metabolism. An overview of the metabolic aspects of several monoamine oxidase inhibitors, including phenelzine, tranylcypromine, pheniprazine, pargyline and deprenyl, is presented. 2. There is still considerable controversy surrounding the role of acetylation in the metabolism of phenelzine. The possibility of ring hydroxylation as well as the formation of beta-phenylethylamine, phenylacetic acid and rho-hydroxyphenylacetic acid from phenelzine is explored. 3. Tranylcypromine has been shown to undergo acetylation and ring hydroxylation. Opening of the cyclopropyl ring is also possible, although this still remains a matter of debate. The pharmacological activity and pharmacokinetic properties of the enantiomers of tranylcypromine are discussed. Chemical substitution in the 4-position of the phenyl ring has been utilized in the design of tranylcypromine analogues with potential antidepressant activity. 4. The formation of amphetamine from pheniprazine and the metabolism of the N-propargyl drugs pargyline and deprenyl are discussed.

Animals↗

PubMed2003

Catechol-O-methyltransferase and monoamine oxidase A genotypes and drug response to conventional neuroleptics in schizophrenia.

Biogenic amine synthesis and degradation are involved in the pathogenesis of schizophrenia. Catechol-O-methyltransferase and monoamine oxidase enzymes are important agents in the metabolic inactivation of these neurotransmitters (ie, dopamine, serotonin, and norepinephrine). Functional polymorphism in the catechol-O-methyltransferase and monoamine oxidase A genes causes variation in enzyme activities. We investigated the relationship of catechol-O-methyltransferase Val158Met and monoamine oxidase A promoter repeat polymorphism with response to conventional neuroleptic treatment in schizophrenia.Ninety-four schizophrenic patients formed 2 different study populations. The responders had experienced a fair and steady response to conventional neuroleptics. The nonresponders had failed to achieve an acceptable response to conventional neuroleptics. We also used a control population of 94 age-matched and gender-matched blood donors. Genotyping of the catechol-O-methyltransferase and monoamine oxidase A genes was performed by polymerase chain reaction.Forty-three percent of the nonresponders had a low activity catechol-O-methyltransferase genotype compared with 16% of the responders (P = 0.009). Monoamine oxidase A genotype alone did not differ significantly between the groups. Moreover, the risk of having both low-activity catechol-O-methyltransferase and monoamine oxidase A genotypes was over 6 times more common (odds ratio = 6.16, P = 0.03) in the nonresponders compared with responders. The whole population of patients with schizophrenia did not differ from the controls.The low-activity catechol-O-methyltransferase genotype may be associated with unsatisfactory drug response to conventional neuroleptics or alternatively be involved in a subset of schizophrenics. The role of monoamine oxidase A genotype seems to be additive in this respect.

Adult↗

PubMed1982

The nature of inhibition of thyroid monoamine oxidase by thyroxine in rat thyroid.

The effect of thyroxine on rat thyroid monoamine oxidase (MAO) activity in vivo and in vitro was studied in order to evaluate the nature of the inhibition of the enzyme. Monoamine oxidase activity was measured in rat thyroid homogenate. Thyroxine (200 micrograms kg-1) or triiodothyronine (40 micrograms kg-1) injected in vivo inhibited the activity of monoamine oxidase (MAO) significantly (P less than 0.05). Thyroxine (T4), 10 micrograms added to the incubation mixture during 20 min also inhibited MAO activity in thyroid homogenate. A Lineweaver-Burk plot of the data obtained shows that the inhibition is of the uncompetitive type.

Animals↗

PubMed2002

Increased monoamine oxidase messenger RNA expression levels in frontal cortex of Alzheimer's disease patients.

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common cause of dementia in the industrialised world. The two monoamine oxidase (MAO) enzymes, monoamine oxidase A (MAOA) and monoamine oxidase B (MAOB), are important in the metabolism of monoamine neurotransmitters. AD and ageing have been shown to increase enzyme activity for both MAOA and MAOB. An increase (rather than decrease) of enzyme activity is a rare event in a disease that results in a decrease in the number of cells in the brain. The mechanism, transcriptional or post-transcriptional, responsible for the increase in protein activity, is not known. In this study, we investigate for the first time the messenger RNA (mRNA) expression levels of both MAOA and MAOB in 246 cortical brain samples obtained at autopsy from 62 AD patients and 61 normal controls. We found a significant increase in mRNA levels for both MAOA (P=0.001) and MAOB (P=0.002) in disease brain tissue. This indicates that both MAO enzymes might be important in the progression of AD.

Adolescent↗

PubMed1981

Type A monoamine oxidase catalyzes the intraneuronal deamination of dopamine within nigrostriatal, mesolimbic, tuberoinfundibular and tuberohypophyseal neurons in the rat.

Clorgyline (0.3-10 mg/kg, i.p.) inhibited type A monamine oxidase (5-hydroxytryptamine as substrate) but not type B monoamine oxidase (phenylethylamine as substrate) in homogenates of rat striatum and olfactory tubercle; deprenyl (0.3-3 mg/kg, i.p.) inhibited type B but not type A monoamine oxidase in these homogenates. The same doses of clorgyline increased concentrations of dopamine in striatum, and dopamine and norepinephrine in the olfactory tubercle, median eminence and posterior pituitary; they also reduced the concentrations of dihydroxyphenylacetic acid and the rate of synthesis of dopamine (DOPA accumulation after a decarboxylase inhibitor) in the same brain regions. On the other hand, the administration of deprenyl at doses that markedly inhibited type B monoamine oxidase did not alter the concentrations of dopamine, norepinephrine and dihydroxyphenylacetic acid or the rate of accumulation of DOPA in these brain regions. In addition, only clorgyline significantly lowered serum concentrations of prolactin. These results that type A monoamine oxidase catalyzes the intraneuronal deamination of dopamine within terminals of nigrostriatal, mesolimbic, tuberoinfundibular and tuberohypophyseal dopamine neurons.

Animals↗

PubMed1988

Determination of platelet monoamine oxidase by new continuous spectrophotometric method.

A simple, continuous spectrophotometric method for the determination of tissue monoamine oxidase based on the oxidation of 2,2'-azino-di-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) using peroxidase has already been described (Ivanović, I. & Majkić-Singh, N. (1986) Fresenius Z. Anal. Chem. 324, 307). In the present study the method is optimised for platelet monoamine oxidase assay and applied to healthy persons and schizophrenic patients. The obtained data were statistically analysed. The continuous ABTS method is sensitive, precise (CV below 6.9%) and linear up to 83 U/g protein. Comparison with the end-point method of Szutowicz et al. (1984) Anal. Biochem. 138, 86-94) gave a good correlation (r = 0.983). The reference values for the activity of human platelet monoamine oxidase by the new continuous ABTS method are 25 to 42 U/g protein (means = 33.2 U/g protein, CV = 15.5%, n = 67). No differences were found between females and males, or between three age groups ranging from 21 to 52 years. The patients with chronic (n = 76) or acute (n = 17) schizophrenia had significantly lower monoamine oxidase activities compared with normal values (p less than 0.005), which indicates that platelet monoamine oxidase can be a possible marker for schizophrenic diseases.

Adult↗

PubMed1975

Platelet monoamine oxidase in children with infantile autism.

Platelet monoamine oxidase activity was measured in 9 autistic subjects and 9 controls. There were no significant differences in the rates of metabolism of 5-hydroxytryptamine, dopamine or tyramine between the two groups, although the rate of metabolism of tyramine was more rapid than 5-hydroxytryptamine or dopamine within each group. It is concluded that the data presented do not support the view that measurement of platelet monoamine oxidase can be used as a biochemical index to aid in the clinical diagnosis of infantile autism.

Adolescent↗

PubMed1991

Changes in the plethysmogram patterns of finger reactive hyperemia in nutritional (alcoholic) liver disease patients with increased serum monoamine oxidase activities.

The activity levels of serum monoamine oxidase in nutritional (alcoholic) liver disease patients were elevated beyond the upper normal limit, while those of other subjects without pathologically accelerated fibrosis ranged within normal values. Capillaroscopic and plethysmographic studies on finger reactive hyperemia revealed that two characteristic changes in the blood microcirculation, which indicated an occurrence of increased fibritic process in the capillary wall and skin tissues, were observed only in the nutritional (alcoholic) liver disease patients with the elevated serum monoamine oxidase levels. These results suggested that nutritional (alcoholic) liver disease is not a disease restricted to liver tissues, but to a disorder creating pathological fibrosis in the whole-body.

Adolescent↗

PubMed1974

Monoamine oxidase and cerebral uptake of dopaminergic drugs.

The brain uptake of amines that do not enter the brain or enter it poorly was promoted by noncompetitive inhibitors of monoamine oxidase, as shown by behavioral and chemical criteria. Mice pretreated with water or enzyme inhibitors other than those mentioned were placid after receiving dopamine (3,4-dihydroxyphenethylamine). Mice pretreated with monoamine oxidase inhibitors (nialamide or iproniazid) showed upon treatment with dopamine the brisk motor responses characteristic of treatment with its precursor, L-dopa (3,4-dihydroxyphenylalanine). After receiving dopamine, intact nialamide-pretreated mice showed marked increases of brain dopamine, in contrast to water-pretreated test mice or water-treated controls. In unilaterally caudectomized, nialamide-pretreated mice, dopamine induced marked lateral curving of the body toward the lesion followed by running in that direction. Noradrenaline or adrenaline induced curving in caudectomized mice, whereas intact ones remained placid.These catecholamines are bound and inactivated by monoamine oxidase. The cerebral uptakes of chemicals that are bound but not inactivated by monoamine oxidase were thereafter tested. Nialamide induced increased behavioral responses to apomorphine and to N-propyl noraporphine, increased cerebral concentrations of both, and a deep coloration of the brain from methylene blue (bound by monoamine oxidase) but not Evans blue (bound by albumin). Even large doses of nialamide, however, failed to affect the behavioral responses to oxotremorine, which has cholinergic rather than adrenergic or dopaminergic properties. Mitochondrial monoamine oxidase seems therefore to play a specific regulatory role in the transport of substances that it binds, either to inactivate or to release them.

Animals↗

PubMed2003

Monoamine oxidases: to inhibit or not to inhibit.

Monoamine oxidase (MAO) inhibitors were developed as antidepressants but many drugs, including the novel oxazolidinone antibacterial agents, share similar molecular properties and have MAO inhibitory activity. Factors important for binding antidepressants and modifications to decrease binding of oxazolidinones to avoid undesirable vascular effects are discussed.

Animals↗

PubMed1961

Histochemical demonstration in rat of monoamine oxidase inhibition of beta-phenyl-isopropyl hydrazine.

A histochemical method for demonstration of monoamine oxidase activity was found to be almost as sensitive as a biochemical method when used for revealing total inhibition of monoamine oxidase in rat tissues after administration of beta-phenyl-isopropyl hydrazine. The histochemical method is of special value in the study of monoamine oxidase inhibition in the complex structures of the brain.

Animals↗

PubMed1993

Association of a monoamine oxidase B allele with Parkinson's disease.

Monoamine oxidase B (MAO-B) is implicated in the cause of Parkinson's disease (PD) because of its role in metabolizing the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and forming H2O2 during dopamine metabolism. Altered MAO-B activity has been observed in PD platelets. Polymerase chain reaction was used to amplify a portion of the MAO-B gene. Polymerase chain reaction products were screened with restriction enzymes to identify fragments useful for single-stranded conformational polymorphism analysis. A single-stranded conformational polymorphism was identified in an MAO-B polymerase chain reaction product after Hae III digestion. One hundred twenty-one control individuals were allelotyped with frequencies of 0.45 and 0.55 for alleles 1 and 2, respectively. Frequencies of 0.62 and 0.38 (1 and 2, respectively) were observed in a population of 46 patients with PD. The presence of MAO-B allele 1 is associated with a relative risk for PD of 2.03-fold (confidence interval, 1.44-2.61; p < 0.02). For comparison, a monoamine oxidase A polymorphism was used to determine allelic frequencies in these same populations and no statistically significant differences were found. These results suggest that an inherited variant of MAO-B may be involved in a genetic predisposition for PD.

Aged↗

PubMed1999

[Monoamine oxidase, tribulin, isatin: basic and applied medical aspects].

Monoamine oxidase (MAO) catalyzes the biological degradation of the neurotransmitters monoamines. The altered substrate specificity of MAO may be of pathogenic importance in some cases and MAO inhibitors showed a therapeutical effect in the experimental setting. Analyzing the efficacy of various compounds in inhibiting MAO A and B revealed new approaches to designing new-generation MAO inhibitors. Tribulin is a fraction of endogenous MAO inhibitors that are present in human and animal tissues and biological fluids. Isatin is an endogenous indole which was initially derived from a tribulin fraction. An investigation of the biological properties of tribulin revealed its heterogeneity and some chemical components were identified. It was shown that deficiency of tribulin components that selectively inhibited MAO A long with a larger number of molecules of this enzyme might be of great importance for the development of alcoholism. In addition to MAO inhibition, the physiological concentrations of isatin inhibited the receptor-binding of atrial natriuretic peptides and ANP-stimulated guanylate cyclase (GC). The sensitivity of ANP-GC to isatin might be allosterically regulated. Selective antagonists of natriuretic peptide receptors were found among isatin analogues which may be an effective pharmacological tool for further studies of the role of natriuretic peptides in the body.

Adrenal Cortex↗

PubMed1984

Properties of monoamine oxidase in monkey heart.

The activities of monoamine oxidase (MAO) in a homogenate and the mitochondrial fraction of monkey (Macaca fascicularis) heart were measured with labelled benzylamine, serotonin (5-HT), tyramine and beta-phenylethylamine (PEA) as substrates. The effects of clorgyline, deprenyl and semicarbazide on MAO were also investigated. Benzylamine deamination was more sensitive to deprenyl than to clorgyline, although it was not completely inhibited by a high concentration of either, and the remaining activity was completely inhibited by pretreatment with semicarbazide. The activities of 5-HT and tyramine were both more sensitive to clorgyline than to deprenyl, and both inhibitors gave single-sigmoidal inhibition curves. Experiments with increasing concentrations of PEA as substrate and clorgyline and deprenyl as inhibitors indicated that at higher concentrations, PEA was a substrate for MAO-A as well as MAO-B in monkey heart. These results suggest that monkey heart mitochondria contain not only MAO-A and MAO-B, but also clorgyline resistant amine oxidase (CRAO). The ratio of MAO-A, MAO-B and CRAO was determined from plots of inhibitions with each substrate. The kinetic constants of MAO in monkey heart were compared with those of MAO in hearts of other animals. The enzymic properties of MAO in monkey heart were discussed on the basis of these results.

Animals↗

PubMed1977

Properties of monoamine oxidase (MAO) in human blood platelets, plasma, lymphocytes and granulocytes.

The properties of monoamine oxidase in plasma, platelets, lymphocytes and granulocytes have been studied using cells prepared from a single small (about 20 ml) sample of blood. The three substrates, 5-hydroxytryptamine, tyramine and benzylamine, have been used to obtain a more complete picture of blood monoamine oxidase than was previously possible. Measurement of Michaelis constants, use of selective inhibitors, and activity against the three substrates distinguished three types of activity. The monoamine oxidases in platelets and lymphocytes are very similar, being most active with tyramine or benzylamine as substrate and inhibited by low concentrations of deprenil. The enzymes in plasma and granulocytes are similar in their relatively high activity against 5-hydroxytryptamine and in their inhibition by semicarbazide and cuprizone with tyramine or benzylamine as substrates. They differ in their affinities for 5-hydroxytryptamine and their activity against tyramine. The activity in platelets, plasma, lymphocytes and granulocytes has been measured in a group of 15 normal subjects using three substrates.

Adult↗

PubMed1996

Localization of monoamine oxidases in human peripheral tissues.

Localization of monoamine oxidases (MAO) A and B and beta-adrenoceptors, was studied in aged human peripheral tissues (age 68-80 years) by quantitative autoradiography. The tissues analyzed were heart, lung, liver, kidney, spleen and duodenum. [3H]Ro41-1049 and [3H]lazabemide, two recently characterized selective radioligands were used to map MAO-A and MAO-B respectively. The regional pattern of distribution of MAO-A and MAO-B did not differ markedly, except in kidney and especially in duodenum. Highest levels of MAOs were measured in liver, and lowest in spleen. MAO-A was more abundant than MAO-B in lung and duodenal mucosa, and the reverse was true in myocardium. These results show marked differences in the abundance and patterns of distribution of MAOs, particularly MAO-B, in human and rodent peripheral tissues.

Aged↗