Monoamine Oxidase Activity Levels Research Articles

The determination of the catecholamines and their metabolites in the pedal ganglion of Quadrula pustulosa (Mollusca, Pelecypoda)

1. 1. Dopamine represents the only catecholamine present in the pedal ganglion of the freshwater pelecypod Quadrula pustulosa detectable by ascending thin-layer chromatography. 2. 2. Dihydroxyphenylacetic acid and an unknown compound appear to be the only metabolites of dopamine. 3. 3. Pedal ganglia concentrate dopamine when incubated in a solution containing the amine. 4. 4. Concentration of [ 3H]dopamine occurs within neurons, as demonstrated by light microscope autoradiography. 5. 5. Determination of the rate of conversion of [ 3H]dopamine to dihydroxyphenylacetic acid (2.33 × 10 −4 μg. per g. per hour) indicates low levels of monoamine oxidase activity.

Dopa-decarboxylase in autonomic and sensory ganglia of the cat.

AbstractAs far as dopadecarboxylase (DDC) activity is concerned sympathetic ganglia can be collected into 3 groups: celiac and superior mesenteric show the highest activity, superior cervical and stellate are intermediate, lumbar and sacral ganglia show the lowest activity. Ciliary and nodose ganglia show significantly lower DDC activity than sympathetic ganglia and spinal ganglia show no measurable activity. There is a good correlation between DDC activities, monoamineoxidase (MAO) activities and the catecholamine contents of autonomic ganglia. Preganglionic de‐nervation did not significantly change DDC, MAO or catechol‐O‐methyltransferase (COMT) activity of L.r ganglia. It is concluded that although MIAO and DDC are not exclusively as sociated with adrenergic neurons, a high level of DDC or MAO activity in the cell body is a specific attribute of adrenergic neurons.

Enzyme histochemistry and hormones of the developing gastrointestinal tract of the chick embryo. II. The histochemistry of oxidative enzymes.

In this investigation glueagon has been histochemically demonstrated by the fluorescent antibody technique in the developing gastrointestinal tract of the chick embryo. The levels of monoamine oxidase activity at various stages during the development of the gastrointestinal tract has been studied. Both monoamine oxidase activity and argentaffin positive cells have been demonstrated histochemically in the epithelial cells of the embryonic stomach-complex and intestine. This similarity in the localisation suggests that monoamine oxidase activity may be related with the seratonin producing cells.

Multiple substrate determination of monoamine oxidase distribution and iproniazid inhibition in rat brain.

Abstract— —A variety of monoamine oxidase substrates (tyramine, dopamine, serotonin, tryptamine) have been used with and without Iproniazid inhibition to evaluate further the extent to which enzyme multiplicity may exist in various regions of rat brain. Levels of monoamine oxidase activity, as measured by ammonia production, were found to vary as a function of both brain area and kind of substrate used, in the absence as well as in the presence of Iproniazid, in vivo and in vitro. Similarity of substrate metabolizing patterns among the different brain areas, however, strongly suggests that only one kind of monoamine oxidase exists in rat brain.

Urinary dopamine levels and kidney monoamine oxidase activity in hypertensive rats

The relationship among urinary dopamine levels, arterial blood pressure, and kidney monoamine oxidase (MAO) activity was studied in male rats with experimentally induced renal hypertension. Urinary dopamine levels rose throughout the experimental period from an average control value of 673 μg/l to a high of 1,022 μg/l. The excretion of dopamine was found to be quite variable. A regression analysis was conducted by regressing blood pressure on logarithm dopamine concentration. The coefficient of regression was + 0.85. As the weight of the experimental (hypertensive) animals increased, the urinary dopamine levels (μg/kg/24 hr) increased, whereas in the sham-operated control animals, the urinary excretion of dopamine (μg/kg/24 hr) decreased with increasing weight. Kidney MAO activity decreased after the induction of hypertension, went through what appeared to be a compensatory rise, and then dropped off sharply to the end of the experimental period. A clear and consistent relationship between decreased MAO activity and urinary dopamine levels was not established.

THE ROLE OF RIBOFLAVIN IN MONOAMINE OXIDASE ACTIVITY

The role of riboflavin in the activity of monoamine oxidase (MAO) was investigated by omitting the vitamin from the diet of rats which were further treated with iproniazid, an irreversible inhibitor of the enzyme. The rate of recovery from the inhibition, presumably reflecting de novo synthesis of the enzyme, was estimated by measuring the excretion of the acidic metabolites formed after intraperitoneal administration of serotonin (5 HT) and dopamine. Consumption of the deficient diet did not impair the action of MAO on these amines. After injection of iproniazid, return to control levels of MAO activity was slower when measured by the oxidation of dopamine than of 5 HT; there was a small but significant effect of riboflavin deficiency upon the conversion of 5 HT to 5-hydroxyindoleacetic acid. This was probably due to enhanced inhibition of MAO observed in deficient rats, an effect that was also obtained when inhibitors other than iproniazid were used in vivo. Similarly, disappearance of 5 HT during incubation with a supernatant prepared from liver of deficient rats was also affected to a greater extent by these inhibitors than when the enzymatic system was prepared from control livers. This finding suggests that riboflavin deficiency renders MAO more susceptible to inhibition.

THE ROLE OF RIBOFLAVIN IN MONOAMINE OXIDASE ACTIVITY

The role of riboflavin in the activity of monoamine oxidase (MAO) was investigated by omitting the vitamin from the diet of rats which were further treated with iproniazid, an irreversible inhibitor of the enzyme. The rate of recovery from the inhibition, presumably reflecting de novo synthesis of the enzyme, was estimated by measuring the excretion of the acidic metabolites formed after intraperitoneal administration of serotonin (5 HT) and dopamine. Consumption of the deficient diet did not impair the action of MAO on these amines. After injection of iproniazid, return to control levels of MAO activity was slower when measured by the oxidation of dopamine than of 5 HT; there was a small but significant effect of riboflavin deficiency upon the conversion of 5 HT to 5-hydroxyindoleacetic acid. This was probably due to enhanced inhibition of MAO observed in deficient rats, an effect that was also obtained when inhibitors other than iproniazid were used in vivo. Similarly, disappearance of 5 HT during incubation with a supernatant prepared from liver of deficient rats was also affected to a greater extent by these inhibitors than when the enzymatic system was prepared from control livers. This finding suggests that riboflavin deficiency renders MAO more susceptible to inhibition.