L. Cronenberger

Activation by S-adenosylhomocysteine of norepinephrine and serotonin in vitro uptake in synaptosomal preparations from rat brain.

S-Adenosylhomocysteine (10−7−10−5 M) activated norepinephrine (NE) and serotonin (5HT) in vitro uptake in synaptosomal preparations from rat brain, but did not affect dopamine (DA) uptake. When administered to rats (7 mg/kg i.p.), it had the same effect on in vitro NE and 5HT uptake. It did not affect NE and 5HT release.

Purification et propriétés de la diamine: oxygène oxydo-reductase du placenta humain

Summary Histaminase or diamine: oxygen oxydoreductase (E.C.1.4.3.6.) has been purified 9,600 times from human placenta. The major difficulty was to eliminate hemoglobin from the extracts. In addition, the enzyme has to be stabilized by sucrose during the last steps. As fractionation progresses, a latency time up to 3 h 30 mn modifies the enzymatic kinetic. This latency time is annihilated by preincubation without histamine at 37°C. The enzyme requires Mn++ ions and hemoglobin; there is a potentiating effect for these activators. The isoelectric point is near 6.0 and histaminase is unstable at this pH. The optimum pH is 7.4. The optimum temperature is superior to 45°C. Filtration on Biogel reveals 4 active forms whose molecular masses are multiples from 1 to 4 of 125,000 ± 5,000. Apparent Michaelis constants determined for histamine, putrescine and cadaverine are respectively 0.6 × 10−5 M, 3.3 × 10−6 M and 3.3 × 10−6 M. Histaminase is inhibited by excess histamine but other diamines do not entail this result. Monoamines are not altered by the enzyme. Aminoguanidine is the best inhibitor; semicarbazide is much less active. According to several of its physico-chemical characteristics, diamine: oxygen oxydoreductase from human placenta is different from similar enzymes already described.

Purification et detection de plusieurs formes moleculaires de l'histidine decarboxylase de la muqueuse gastrique de rat

Abstract A specific histidine decarboxylase from rat gastric mucosa has been obtained at high purity and good yield (purification about 600-fold). The purification procedure included double (NH4)2SO4 fractionation, ion-exchange chromatography, preparative isoelectric focusing in a granulated gel and gel filtration. Only the specific histidine enzyme was obtained by that procedure; DOPA decarboxylase, a non-specific enzyme, was absent in our final preparation. Each step of the purification was visualized by polyacrylamide gel electrophoresis and analytical isoelectric focusing. The purified enzyme was apparently homogeneous by criteria of electrophoresis and gel filtration and has a molecular weight of 94 000. Several protein bands appeared after isoelectric focusing and the enzyme activity was localized in 3 distinct peaks. The gastric enzyme consists of 3 active forms which could be distinguished by their isoelectric points: 5.4, 5.75 and 6. Molecular weights estimated by SDS polyacrylamide gel electrophoresis were 97 000, 93 000 and 90 000, and no subunits were observed. Pyridoxal phosphate was required as a coenzyme and resolution of the holoenzyme agreed with a portion of the coenzyme tightly bound to the apo-enzyme. The purified enzyme was stable at low ionic strength, near neutral pH; concentrated reducing agents inhibit the enzyme.

Monoamine oxydase dans les homogénats d'organes

Summary The monoamine oxydase activity of rat heart, liver, kidney and brain homogenates has been determined by a new technique. The principle is as follows: benzylamine is used as a substrate, then after incubation, the proteins of the medium are precipitated and the benzaldehyde formed is extracted with cyclohexane. Optical density of the cyclohexane solutions is measured at 242 nm, corresponding to the maximum absorption of benzaldehyde in this solvent. The technique is especially interesting for an assay in heart or kidney, as benzaldehyde spectrophotometry in an aqueous medium is inaccurate.

Identification de la 4-O-méthyl dopamine dans les tissus de rat par chromatographie liquide en phase inverse

Identification of 4-O-methyldopamine in rat tissues by reversed-phase liquid chromatography 4-O-Methyldopamine was identified and assayed in tissues from l-dopa treated rats by reversed-phase high-performance liquid chromatography. The initial steps in the separation of catecholamines were performed by alumine, a weak cation-exchange resin, and thin-layer chromatographic techniques. After L-[3H] dopa administration, the radiochromatogram was superimposed on the fluorochromatogram obtained with authentic marker 4-O-methyldopamine. This metabolite was detected in kidney but not in brain. The 4-O-methyldopamine:3-O-methyldopamine ratio was 0.032 in kidney. The influence of various treatments on this ratio was investigated. A 160% increase was found after l-dopa administration. This effect was potentiated by nialamide pretreatment (550% increase).

Effet De La S-Adenosyl-L-Homocysteine Sur Le Catabolisme De La Dopamine

Abstract1.—The administration of SAH to rats, at physiologically active dose on the sleep, does not change the urinary level of MD and NM. On the other hand, the excretion of DA and NA decreases.2.—In the brain, SAH does not modify neither the concentration of NA and NM in hypothalamus and thalamus, nor the concentration of DA and MD in corpus striatum.3.—After intracisternally injection of [14C]DA or PH]NA, SAH increases the level of [14C]MD and [3H]NM.4.—Contrary to the studies in vitro, where SAH is an inhibitor of COMT, on the rat it does not seem prevent the methylation of DA and NA.

Effet De La S-Adénosyl-L-Méthionine Sur Le Métabolisme Cérébral Et Périphérique De La L-Dopa(1)

AbstractThe repartition of [3H]L-dopa administred i.p. does not change in rats treated with 5-adenosyl-L-methionine (SAM). The effect was studied on the central nervous system and at the periphery. The biosynthesis of metabolites [3H]dopamine and [3H]3-O-methyldopamine are also unchanged.On the other hand, in the kidney an accumulation of [3H]norepinephrine +[3H]normetanephrine was observed, while in the brainstem + midbrain the synthesis of these metabolites was decreased after SAM injection.The relations between these biochemical results and the pharmacological antiparkinsonian effects are discussed.