Uptake of adrenaline by rat brain synaptosomes. Effects of several psychotropic drugs]

Comparative study of the uptake of 3H-epinephrine (3H-EN) and 3H-norepinephrine (3H-NE) into rat brain crude synaptosomes and effect of psychotropic drugs of different classes on this process showed that isolated nerve terminals had their own transport system for EN. The crude synaptosomal fraction had two transport system's for EN; high-specific active uptake with high affinity (KM = 3.7 + 0.21 microM) and low-affinity uptake (KM2 = 98.0 + 47.5 microM). En accumulation was saturable, stereo-specific and inhibited by ouabain (3 X 10(-3) M), protoveratrine A and B (10(-4) M), NaN3 (2 X 10(-3) M), 2,4-dinitrophenol (2 X 10(-3) M), p-chloromercuribenzoate (10(-4) M). Actinomycin D had no effect on the uptake of 3H-EN. 3H-HE was accumulated by two uptake system: 1-high affinity uptake system with KM values of 0.49 + 0.13 microM, 2-low affinity uptake system with KM values of 21.1 + 7.71 microM. Amphetamine, mesocarb, chlorpromazine, fluphenazine and haloperidol were equally effective inhibitors of 3H-EN and 2H-HE uptake. Imipramine, phenazepam, diazepam and carbamazepine (5 X 10(-5) M) had no effect on the uptake of 3H-NE. Imipramine, zimelidine, norzimelidine and viloxazine (5 X 10(-5) M) were more potent inhibitors of the 3H-EN uptake than that of 3H-NE.     

Effect of ultrasound on the ATPase activity of brain microsomes

Ultrasonic effects (0.88 MHz, 0.8 Wt X cm-2) on Na+, K+-ATPase and Mg2+-ATPase changed the values KM, Vmax, delta H not equal to, delta S not equal to and the activation energy, which can point to some changes in the structure of lipoprotein enzyme complexes.     

Effect of carbacholine and serotonin on the ATPase activity in synaptosomes of the projection and association areas of the feline cerebral cortex]

Na, K-ATPase and Mg-ATPase activities were measured in the synaptosomes of the temporal auditory projection area and the frontal association area. Moreover, the effects of carbacholine and serotonin on those activities were investigated. Na, K-ATPase activity in the synaptosomes of the association area was shown to be reliably higher that in the synaptosomes of the projection area (11.02 +/- 0.45 vs 8.40 +/- 0.55 microM Pi/mg of protein hr; P less than 0.05). Mg-ATPase activity was higher in the second case as compared to the first one (11.40 +/- 0.38 vs 9.04 +/- 0.35; p less than 0.05). Carbacholine and serotonin (10(-8)-10(-3) M) were found to induce equal inhibition of Na, K-ATPase activity in the synaptosomes of both cortices (1 max = 25-30%, 1C50 = 0.2-0.3 microM) which is blocked respectively with atropine (10(-6) M) and methysergide (10(-6) M) and enhanced in presence of GTP (5.10(-5) M). The enzyme activity is also inhibited by the non-hydrolysable guanine nucleotide, GTP gamma S (10(-8)-10(-4) M), in the absence of the antagonists (1 max = 35-40%, 1 C50 = 0.02 microM). In the methysergide-containing medium serotonin exerts a dose-dependent stimulatory effect on Na, K-ATPase which is more pronounced in the synaptosomes of the association area (A max = 25%, A C50 = 0.05 microM). Mg-ATPase activity of membrane preparations is liable to be stimulated by both serotonin and carbacholine, stimulation being more pronounced in the synaptosomes of the association cortex as well (A max = 35%, A C50 = 0.2-0.3 microM). This effect is insensitive either to the antagonists of the corresponding receptors or to GTP. GTP gamma S does not cause alterations in the enzymatic activity. Na, K-ATPase is suggested to be coupled to muscarine and serotonin receptors in the synaptic membranes of both projection and association cortical areas via a GTP-binding protein. At the same time, the agonists of receptors mentioned above are presumably also capable to effect Mg-ATPase activity by the receptor-independent way.     

The inhibitory effect of aluminium on the (Na+/K+)ATPase activity of rat brain cortex synaptosomes

The effect of AlCl(3) on the (Na(+)/K(+))ATPase activity of freeze-thawed synaptosomes, isolated from rat brain cortex, has been studied. The AlCl(3) action on the enzyme hydrolytic activity was examined using in vitro and in vivo approaches. Following exposure to AlCl(3) using both in vitro (synaptosomes incubated in the presence of AlCl(3) for 5 min) and in vivo (synaptosomes isolated from rats that received 0.03 g AlCl(3)/day for 4 months) approaches, the (Na(+)/K(+))ATPase activity was inhibited in a concentration-dependent way. The maximal inhibitory effect (approximately 60%) was observed in the presence of a AlCl(3) concentration >75 microM and at non-limiting ATP concentrations. Conversely, AlCl(3) did not inhibit the enzyme activity when UTP was used as substrate instead of ATP. Analysis of the substrate dependence of membrane-bound (Na(+)/K(+))ATPase by a computer simulation model suggests that the AlCl(3)-induced inhibitory effect is characterised by a reduction of the rate-limiting step velocity of the reaction cycle. Moreover, it seems that aluminium can induce impairment of the interprotomeric interaction within the oligomeric ensemble of membrane-bound (Na(+)/K(+))ATPase. In fact, this effect was accompanied by a slight, but significant, decrease of readily accessible SH groups, which are involved in the maintenance of the membrane-bound (Na(+)/K(+))ATPase oligomeric structure. In conclusion, during exposure to aluminium, reduction of the activation of membrane-bound (Na(+)/K(+))ATPase by high ATP concentrations occurs, which results in a partial inhibition of the enzyme.     

Effect of neurocatin on the activity of monoamine oxidase B in rat brain synaptosomes

Neurocatin, a small (about 2,000 Dalton) neuroregulator isolated from mammalian brain, is a powerful effector of monoamine oxidase B in rat brain synaptosomes. Incubation of intact synaptosomes with neurocatin caused an inhibition of the enzyme dependent on the concentration of neurocatin. This inhibition became statistically significant at a neurocatin concentration of 10 ng/200 l and was significant at all higher neurocatin concentrations. At 40 ng/200 l, neurocatin inhibited monoamine oxidase B activity by about 60%. This inhibitory effect was almost completely abolished by breaking the synaptosomal membrane by hypotonic buffer prior to incubation with neurocatin. In addition, incubation of the synaptosomes in calcium free medium almost completely abolished the inhibitory effect of neurocatin on monoamine oxidase B. The inhibition appeared to involve covalent modification of the enzyme mediated by a neurocatin receptor(s). Measurements of the kinetic parameters of the enzyme showed that 20 ng of neurocatin caused a statistically significant decrease in V_max (by 20%) with no significant change in K_M, compared to controls. Inhibition of monoamine oxidase by neurocatin is potentially of great clinical importance because this enzyme plays a major role in catabolism of the biogenic amines and alterations in its activity is believed to contribute to several neurological disorders.     

Analysis of the brain bioelectrical activity of the suslik Citellus parryi during hibernation

Computer analysis has been made of the diurnal rhythm of the brain activity in the ground squirrel Citellus parryi during hibernation (body temperature 7-8 degrees C). The data obtained are presented in the form of graphical plots with two-dimensional density of probability of distribution of intermittent bursts of spindles and isoelectric EEG.     

Effect of lithium on dopamine uptake by brain synaptosomes

Lithium chloride exerts two opposite effects on dopamine uptake by synaptosomes isolated from rat caudate nucleus. Added in vitro, it inhibits dopamine uptake; whereas administered chronically in vivo, it enhances dopamine uptake in vitro. Thus, in vitro, 1, 2.5, 5 and 10 meqiv.l-1 of lithium chloride decrease [3H]dopamine uptake by 13, 17, 25 and 31%, respectively. Synaptosomes isolated from rats treated with lithium chloride for 20 days, show a 23% increase in [3H]dopamine uptake with respect to synaptosomes isolated from control rats. It is suggested that chronic lithium treatment stimulates a compensatory mechanism which overcomes its direct inhibitory effect on [3H]dopamine uptake.     

Electron-cytochemical study of the localization of ATPase activity in the brain tissue of white rats]

A localization of ATPase activity in a rat's brain was studied by the lead method at the presence of Mg2+. The highest activity was noticed in the capillar basal layer, in nucleoli and nuclear chromatin. Less intensive sedimentation of precipitate was observed on the external nuclear membrane, granular cytoplasmic reticulum, ribosomes and in lipofuscin granules. Besides, the reaction product was observed on the cytomembrane of neurons, in synaptic slits and on the vesicles of some terminals. No ATPase activity was seen in mitochondria in the experimental conditions. Equal distribution of reaction product was seen in the cortex and hypothalamus.     

Effect of altitude hypoxia on ATPase activity in the brain of rats of different ages.

In experiments on 5-day-old and adult rats of both sexes, the authors investigated Na+--K+-stimulated and Mg2+-dependent ATPase activity in the cerebral cortex, subcortical formations and the medulla oblongata. They studied the effect of 20 min acute altitude hypoxia corresponding to either 7,000 or 9,000 m, in a thermostable chamber (30 degrees C). ATPase activity was found to increase during ontogenesis -- this being the greatest in cortical tissue and the least in the medulla oblongata. Hypoxia corresponding to 7,000 m altitude significantly depressed total ATPase activity in 5-day-old rats, but significantly stimulated it in adult animals. Changes in Na+--K+-stimulated ATPase activity played the major role in these changes. Hypoxia corresponding to 9,000 m altitude likewise depressed total ATPase activity in 5-day-old rats and to practically the same extent as moderate hypoxia (7,000 m). In adult rats, marked hypoxia (9,000 m) significantly reduced only Mg2+-dependent ATPase activity. Mg2+ activity rose during ontogenesis to a lesser degree than Na+--K+-stimulated ATPase and the reciprocal ratio of these ATPase and the reciprocal ratio of these ATPase activities, in the given parts of the brain, fell progressively in adult animals to values close to 1.     

Osmotic regulation of the sodium pump in rat brain synaptosomes]

Effect of medium osmolarity on 3H-ouabain binding and the rate of ouabain-sensitive 86Rb+ transport in the rat brain synaptosomes was studied. A decrease in tonicity to 230 mOsm increases both parameters indicating the activation of the sodium pump upon synaptosome swelling. The effect is retained in the absence of inside-oriented Na+ gradient, i. e. a rise in Na(in) is not responsible for hypoosmotic activation. Colchicine (5mM) decreased and cytochalasin B (40 microM) increased the ouabain binding. In the presence of cytochalasin B the inhibition of binding observed under hypotonic conditions was shifted to higher osmolarity values. It is suggested that volume regulation of the sodium pump is controlled by the cytoskeleton elements.     

Effect of organophosphorus insecticides on the oxidative processes in rat brain synaptosomes

Abstract: This paper describes the effect of four organophosphorus insecticides: Dipterex, DDVP, Ronnel and its oxygen analogue on the respiration of rat brain synaptosomes. Dipterex and DDVP in the concentrations used, 5, 50, or 500 μM, did not change the rate of oxygen uptake and oxidative phosphorylation in rat brain synaptosomes. Ronnel in the highest concentration (500 μM) inhibited respiration in state 3 conditions and abolished respiratory control by ADP. This inhibition was correlated with a change of cytochrome c oxidase activity. The oxygen analogue of Ronnel (OAR) in micromolar concentrations (50 μM) increased the rate of respiration of synaptosomes utilizing glutamate plus malate as substrate. Higher concentrations of OAR produced inhibition of respiration, cytochrome c oxidase and NADH: cytochrome c reductase activities. These observations are typical for uncouplers of oxidative phosphorylation. Noteworthy is the fact that the uncoupling activity of OAR was observed at concentrations which did not inhibit acetylcholinesterase activity. These findings seem to suggest that disturbances in oxidative processes could play an important role in the toxicity of organophosphorus insecticides. The relation between chemical structure and the ability of insecticides to affect oxidative phosphorylation is discussed.     

Effect of thymus histones on the RNAase, ATPase and phosphatase activity of staphylococcal cells]

It was shown that the representatives of different strains of Staphylococcus genus were characterized by a differential histone sensitivity. The membrane permeability increased in case of the bacterial contact with histones, and the degrading of the sum total cell RNA occurred in the contact of bacteria with histones. The RNA-ase, phosphatase, and the ATP-ase activity increased in the cells after their treatment with histones. The extent of expression of all these processes in the representatives of different strains correlated with their sensitivity to individual histone fractions. The problem that all the phenomena described indicated both the inhibitory effect of histones and some metabolic changes (permitting the cells to preserve their viability under unfavourable conditions) is discussed.     

Effect of adrenaline on the activity of lipolytic enzymes in calves

The research of adrenalin influence on the lipid synthesis and split intensity and fat acid oxidation was carried out in two groups of one-month old calves of black-white breed. The animals were injected by adrenalin (1 mg/kg) during 3 days. The specimens of the musculus quadriceps extensor femoris were used for biochemical researches. The increase of the triacylglycerol lipase activity and oxidation intensity of [1-14C] palmitic and [1-14C] stearic acids and the reduction of lipoprotein lipase activity and lipid synthesis from acetic acid intensity were found during researches. So, the reciprocal dependence between lipid synthesis and fatty acid oxidation as well as the connection between processes of lipolysis and fatty acid beta-oxidation, influenced by adrenalin, were observed in the skeletal muscles of the cattle.     

Effect of phenobarbital on metabolism of polyphosphoinositides of rat brain synaptosomes

Synthesis and degradation of polyphosphoinositides in a rat brain synaptosome preparation were depressed by phenobarbital. Phosphatidylinositol-4-phosphate kinase (PIP-kinase), the enzyme which synthesizes phosphatidylinositol-4,5-bisphosphate (PIP2) was most strongly affected (50% inhibition at 3 mM phenobarbital); phosphatidylinositol (PI-kinase) followed (50% at 15 mM). The phosphoesterases were less sensitive: PIP-monoesterase (50% at 39 mM), PIP2-monoesterase (at 47 mM), and, least inhibited, PIP-diesterase (50% at 65 mM) and PIP2-diesterase (at 68 mM). Phenobarbital by inhibiting PIP-kinase may reduce the membrane concentration of PIP2 and thus dampen the stimulus-response which leads to the hydrolysis of PIP2 and the formation of the second messenger, inositol-1,4,5-trisphosphate (IP3), involved in mobilization of intracellular Ca2+.