ATPase Activity In Rat Brain Research Articles

Sub‑chronic administration of lead alters markers of oxidative stress, acetylcholinesterase and Na+K+‑ATPase activities in rat brain.

This study investigated the effects of sub‑chronic administration of lead (Pb) acetate on thiobarbituric acid reactive substances (TBA‑RS), total sulfhydryl content, protein carbonyl content, antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GSH‑Px]), acetylcholinesterase (AChE), and Na+K+‑ATPase in the cerebral structures of rats. Male Wistar rats aged 60 days were treated with saline (control group) or Pb (treatment group), at various doses, by gavage, once a day for 35 days. The animals were sacrificed twelve hours after the last administration, and the cerebellum, hippocampus and cerebral cortex were removed. The results showed that Pb did not alter the evaluated oxidative stress parameters. Furthermore, Pb (64 and/or 128 mg/kg) altered SOD in the cerebellum, cerebral cortex and hippocampus. Pb (128 mg/kg) altered CAT in the cerebellum and cerebral cortex and GSH‑Px in the cerebral cortex. Also, Pb (64 mg/kg and 128 mg/kg) altered GSH‑Px in the cerebellum. Moreover, Pb (128 mg/kg) increased AChE in the hippocampus and decreased Na+K+‑ATPase in the cerebellum and hippocampus. In conclusion, sub‑chronic exposure to Pb (occupational and environmental intoxication) altered antioxidant enzymes, AChE, and Na+K+‑ATPase, contributing to cerebral dysfunction.

Carbofuran induced oxidative stress mediated alterations in Na⁺-K⁺-ATPase activity in rat brain: amelioration by vitamin E.

Pesticides cause oxidative stress and adversely influence Na(+)-K(+)-ATPase activity in animals. Since impact of carbofuran has not been properly studied in the mammalian brain, the ability of carbofuran to induce oxidative stress and modulation in Na(+)-K(+)-ATPase activity and its amelioration by vitamin E was performed. The rats divided into six groups received two different doses of carbofuran (15% and 30% LD50) for 15 days. The results suggested that the carbofuran treatment caused a significant elevation in levels of malonaldehyde and reduced glutathione and sharp inhibition in the activities of super oxide dismutase, catalase, and glutathione-S-transferase; the effect being dose dependent. Carbofuran at different doses also caused sharp reduction in the activity of Na(+)-K(+)-ATPase. The pretreatment of vitamin E, however, showed a significant recovery in these indices. The pretreatment of rats with vitamin E offered protection from carbofuran-induced oxidative stress.

ATP Production Rate via Creatine Kinase or ATP Synthase In Vivo

Rationale: 31 P magnetization saturation transfer (MST) experiment is the most widely used method to study ATP metabolism kinetics. However, its lengthy data acquisition time greatly limits the wide biomedical applications in vivo, especially for studies requiring high spatial and temporal resolutions. Objective: We aimed to develop a novel superfast MST method that can accurately quantify ATP production rate constants ( k f ) through creatine kinase (CK) or ATP synthase (ATPase) with 2 spectra. Methods and Results: The T 1 nom (T 1 nominal) method uses a correction factor to compensate the partially relaxed MST experiments, thus allowing measurement of enzyme kinetics with an arbitrary repetition time and flip angle, which consequently reduces the data acquisition time of a transmurally differentiated CK k f measurement by 91% as compared with the conventional method with spatial localization. The novel T 1 nom method is validated theoretically with numeric simulation, and further verified with in vivo swine hearts, as well as CK and ATPase activities in rat brain at 9.4 Tesla. Importantly, the in vivo data from swine hearts demonstrate, for the first time, that within an observation window of 30 minutes, the inhibition of CK activity by iodoacetamide does not limit left ventricular chamber contractile function. Conclusions: A novel MST method for superfast examination of enzyme kinetics in vivo has been developed and verified theoretically and experimentally. In the in vivo normal heart, redundant multiple supporting systems of myocardial ATP production, transportation, and utilization exist, such that inhibition of one mechanism does not impair the normal left ventricular contractile performance.

Lipoic acid blocks seizures induced by pilocarpine via increases in δ-aminolevulinic dehydratase and Na +, K +-ATPase activity in rat brain

In the present study we investigated the effects of lipoic acid (LA) on δ-aminolevulinic dehydratase (δ-ALA-D) and Na +, K +-ATPase activities in rat brain after seizures induction by pilocarpine. Wistar rats were treated with 0.9% saline (i.p., control group), lipoic acid (10 mg/kg, i.p., LA group), pilocarpine (400 mg/kg, i.p., pilocarpine group), or the combination of LA (10 mg/kg, i.p.) with pilocarpine (400 mg/kg, i.p.), 30 min before administration of LA (LA plus pilocarpine group). After the treatments all groups were observed for 1 h. The enzyme activities (δ-ALA-D and Na +, K +-ATPase) were measured using spectrophotometric methods, and the results were compared with that obtained from saline and pilocarpine-treated animals. Neuroprotective effects of LA against seizures were evaluated based on those enzyme activities. The pilocarpine group showed a reduction in δ-ALA-D and Na +, K +-ATPase activities after seizures. In turn, LA plus pilocarpine abolished the appearance of seizures and reversed the decreased in δ-ALA-D and Na +, K +-ATPase activities produced by seizures, when compared to the pilocarpine seizing group. The results from the present study demonstrate that preadministration of LA abolished seizure episodes induced by pilocarpine in rat, probably by increasing δ-ALA-D and Na +, K +-ATPase activities in rat brain during seizures.

Effects of an Acute Treatment with L-Thyroxine on Memory, Habituation, Danger Avoidance, and on Na+, K+-ATPase activity in Rat Brain

Thyroid hormones (THs) have a relevant action on brain development and maintenance. By using an acute treatment to induce a hyperthyroid animal model, we aimed at investigating the effect of an altered THs levels on learning and memory and on the activity of Na(+), K(+)-ATPase in the rat brain. Our results have shown that the acute treatment with L-T4 did not alter the retrieval of the inhibitory avoidance task, but had a significant effect on the elevated plus maze and on open-field performance in rats. We suggest that animals subjected to L-T4 administration improved the habituation to a novel environment as well as a better evaluation of a dangerous environment, respectively. Na(+), K(+)-ATPase activity is increased in parietal cortex (30%), but it is not altered in hippocampus in L-T4 treated group. These both brain structures are involved in memory processing and it was previously demonstrated that there is a double dissociation between them for spatial location information, perceptual and episodic memory. We propose the hypothesis that this increase of Na(+), K(+)-ATPase activity in parietal cortex may be correlated to our results in behavior tests, which suggest a role of THs as well as of the Na(+), K(+)-ATPase in the cognitive process.

Effects of Thyroid Hormones on Memory and on Na+, K+-ATPase Activity in Rat Brain

Thyroid hormones (THs), including triiodothyronine (T3) and tetraiodothyronine (T4), are recognized as key metabolic hormones of the body. THs are essential for normal maturation and function of the mammalian central nervous system (CNS) and its deficiency, during a critical period of development, profoundly affects cognitive function. Sodium-potassium adenosine 5'-triphosphatase (Na(+), K(+)-ATPase) is a crucial enzyme responsible for the active transport of sodium and potassium ions in the CNS necessary to maintain the ionic gradient for neuronal excitability. Studies suggest that Na(+), K(+)-ATPase might play a role on memory formation. Moreover, THs were proposed to stimulate Na(+), K(+)-ATPase activity in the heart of some species. In this work we investigated the effect of a chronic administration of L-thyroxine (L-T4) or propylthiouracil (PTU), an antithyroid drug, on some behavioral paradigms: inhibitory avoidance task, open field task, plus maze and Y-maze, and on the activity of Na(+), K(+)-ATPase in the rat parietal cortex and hippocampus. By using treatments which have shown to induce alterations in THs levels similar to those found in hyperthyroid and hypothyroid patients, we aimed to understand the effect of an altered hyperthyroid and hypothyroid state on learning and memory and on the activity of Na(+), K(+)-ATPase. Our results showed that a hyper and hypothyroid state can alter animal behavior and they also might indicate an effect of THs on learning and memory.

Alterations in Antioxidant Status, Protein Concentration, Acetylcholinesterase, Na+, K+-ATPase, and Mg2+-ATPase Activities in Rat Brain after Forced Swimming

The aim of this study was to investigate whether exercise stress (short [2 h] or prolonged [5 h] forced swimming in rats) could modulate brain total antioxidant status (TAS), tissue protein concentration, and the activities of acetylcholinesterase (AChE), Na +, K +-ATPase, and Mg 2+-ATPase. Protein concentration, TAS and enzyme activities in homogenized rat brain were determined spectrophotometrically. Protein concentration was decreased by 15 % (p < 0.01) and by 30 % (p < 0.001) after 2 h and 5 h of forced swimming, respectively. TAS was decreased by 20 - 25 % after 2 h or 5 h of exercise. AChE was inhibited by 30 % (p < 0.001) and 45 % (p < 0.001) after 2 h and 5 h of forced swimming, respectively. In contrast, Na +, K +-ATPase and Mg 2+-ATPase were stimulated by 80 % (p < 0.001) and 40 % (p < 0.001), respectively, after 2 h of swimming and by 100 % (p < 0.001) and 60 % (p < 0.001), respectively, after 5 h of exercise. Control values in nontreated rats were unaltered (p > 0.05). In conclusion, short or prolonged forced swimming induces oxidative stress in rats, probably resulting in a reduction in brain protein concentration and AChE activity. In addition, a Na +, K +-ATPase and Mg 2+-ATPase activation was observed under the above mentioned experimental conditions. This stress condition may modulate brain intracellular Mg 2+ concentration, neural excitability, metabolic energy production, and neurotransmission.

Lazaroid U-74389G attenuates edema in rat brain subjected to post-ischemic reperfusion injury

The aim of the present study was to determine the potential therapeutic value of 21-aminosteroid U-74389G, on blood–brain barrier (BBB) breakdown and edema in association with the changes in synaptosomal Na +/K + and Mg 2+/Ca 2+-ATPase activities in rat brain subjected to post-ischemic reperfusion injury. Brain ischemia was achieved by means of four-vessel occlusion model for 25 min and animals were sacrificed after 12 h reperfusion. An increase of cerebral tissue water content, blood–brain disruption and the changes of synaptosomal Na +/K + and Mg 2+/Ca 2+-ATPases activities were evaluated. U-74389G was given intraperitoneally at two times as 5 mg/kg at 10 min prior to ischemia and at the beginning of reperfusion. Edema was determined by means of wet-dried weight method, and BBB of extravasation of Evan's blue dye. Extravasation of Evan's blue dye into brain following ischemia and reperfusion was 2.4-fold of control value and brought close to control levels by the effect of U-74389G ( p<0.001). Post-ischemic reperfusion injury caused an increase of 3.7% in tissue water content of whole brain and administration of U-74389G lowered the cerebral edema ( p<0.001). The loses in the Na +/K +-ATPase and Mg 2+/Ca 2+-ATPase activities occurred as 42.1% ( p<0.01) and 65.7% ( p<0.001) of control value, respectively. While Mg 2+/Ca 2+-ATPase activity was enhanced compared to vehicle-treated group of animals ( p<0.01), Na +/K +-ATPase activity was fully recovered when compared to control by U-74389G ( p>0.05). U-74389G also significantly attenuated neuronal necrosis ( p<0.001) which was determined in the hippocampal CA1 subfield. Blood–brain barrier protection, attenuation of brain edema and neuronal necrosis concomitant with the stabilizing of membrane-bound enzymes brought about by the effect of U-74389G suggest that 21-aminosteroids are worthy of consideration in the acute treatment of cerebral ischemia.

Inhibition of calcium ATPase by phencyclidine in rat brain.

Phencyclidine (PCP) is a potent psychotomimetic drug of abuse and has profound effect on the functioning of the central nervous system (CNS). Many of the CNS functions are known to be mediated by calcium (Ca2+). In the present study we have investigated the effects of PCP on Ca2+ ATPase activity in rat brain both in vitro and in vivo. For in vitro studies, synaptic membrane fractions prepared from normal rat brain were incubated with PCP at different concentrations (25-100 microM) before the addition of substrate. For in vivo studies, rats were treated with a single moderate dose of PCP (10 mg/kg, i.p.) and animals were sacrificed at 1,2, 6 and 12 h after treatment. Ca2+ ATPase activity in synaptic membrane fractions was assayed by estimation of inorganic phosphate. PCP inhibited the Ca2+ ATPase in vitro in a concentration dependent manner with significant effect at 50 and 100 microM. A significant time-dependent reduction of the Ca2+ ATPase activity was evident in vivo. As early as 2 h after the treatment of rats with PCP the ATPase activity was significantly reduced. The reduction of Ca2+ ATPase observed even at 12 h after treatment suggesting a prolonged presence of the drug in the brain tissue. Further, kinetic studies in vitro indicated PCP to be a competitive inhibitor of Ca2+ ATPase with respect to the substrate, ATP. The present findings indicate that PCP inhibits synaptic membrane Ca2+ ATPase thus altering cellular Ca2+ homeostasis in CNS which may partially explain the pharmacological effects of the drug and/or its neurotoxicity.

Platelet-activating factor inhibits (Na +,K +) ATPase activity in rat brain

In the present study, experiments were conducted to determine the effect of platelet-activating factor (PAF) on (Na +,K +)ATPase in rat cerebral cortex. PAF, but not lysoPAF, inhibited (Na +,K +)ATPase activity, in a dose- and time-dependent manner, 10 −7 to 10 −6 M being the most effective dose. These effects were abolished in the presence of PCA-4248, a PAF antagonist, indicating that the PAF effect may be mediated by its specific membrane receptors. Omission of external calcium caused an increase in the basal activity and abolished the PAF effect on (Na +,K +)ATPase. The present study demonstrates that PAF inhibits (Na +,K +)ATPase activity in the cerebral cortex and suggests that PAF released during certain pathological conditions, such as ischemia, may act on ATPase. This could be one possible mechanism of PAF action that needs further attention.

Effect of acute starvation on monoamine oxidase and Na+, K+-ATPase activity in rat brain

The activities of monoamine oxidase (MAO), responsible for oxidative deamination of many biogenic amines, and Na+, K(+)-ATPase, which plays a crucial role in the release mechanism of neurotransmitters, were determined in rat brain after acute starvation. They were assayed biochemically from four different regions of the brain in two subcellular fractions. Acute starvation decreased the activity of MAO, whereas the Na+,K(+)-ATPase activity was increased. An effect of starvation was also seen on the blood glucose level, body wt, and the protein content of different brain regions. Starvation or normal dietary fluctuations of certain nutrients that exert precursor influence over neurotransmitter synthesis are important to the brain, and contribute to its regulation of both neuroendocrine response and behavior. A rise in the substrate level, i.e., ATP, as a result of increased utilization of ketone bodies and low level of monoamines in the brain after acute starvation, may be the underlying factor for increasing the activity of Na+,K(+)-ATPase in rat brain. These results suggest that, probably, certain adaptive mechanisms become operative in the brain under disturbed physiological conditions.

Na +/K + -ATPase in rat brain and erythrocytes as a possible target and marker, respectively, for neurotoxicity: studies with chlordecone, organotins and mercury compounds

Due to the inaccessibility of human nerve tissue for direct biochemical evaluation, there appears to be a need to identify peripheral markers which will reflect toxicity to the central nervous system by relatively non-invasive means. The aim of this study was to investigate whether the enzyme Na +/K +-ATPase in erythrocytes could be used as a marker for effects on the same enzyme in brain tissue. The compounds chosen to test this hypothesis were the pesticide chlordecone, the organotin compounds triethyltin and tributyltin, mercuric chloride and methyl mercury. All compounds were found to inhibit in vitro Na +/K + — ATPase activity in rat brain (IC 50s = 0.9–56 μM) and in rat erythrocytes (IC 50s = 1.2–66 μM) with similar potencies. However, administration of these compounds in vivo at high doses produced no significant inhibition of either brain or erythrocyte Na +/K +-ATPase activity, despite observed symptoms of neurotoxicity. Dialysis experiments indicated that dissociation of the compounds by dilution during tissue preparation was not responsible for the lack of detectable in vivo inhibition. Measurements of metal concentrations in brain by atomic absorption spectrometry after in vivo administration of triethyltin, mercuric chloride and methyl mercury indicated that levels of these compounds were too low to inhibit significantly NA +/K +-ATPase activity. These results suggest that inhibition of Na +/K + -ATPase activity might not represent the mechanism responsible for the neurotoxicity of these compounds, and that erythrocyte Na +/K +-ATPase activity is not a useful marker for neurotoxicity following acute exposures.

Effects of systemic kainic acid administration on regional Na+, K+-ATPase activity in rat brain.

Changes in the activity of Na+,K+-ATPase and in the water, Na+, and K+ levels in the parietal cortex, hippocampus, and thalamus were investigated in rats 1, 3, 6, and 24 h following systemic kainic acid injection. An increase in Na+,K+-ATPase activity was observed in all three regions 3 h after the treatment, with a subsequent decrease in enzyme activity. The elevation in Na+,K+-ATPase activity was accompanied by an increase in the Na+ content and a decrease in the K+ content. These changes are presumed to occur because of repeated discharges and excessive prolonged depolarization in response to kainic acid. The decreases in Na+,K+-ATPase activity 6 and 24 h following kainic acid treatment coincide with neuropathological damage and edema formation, mainly in the hippocampus and thalamus.

Altered synaptosomal ATPase activity in rat brain following prolonged in vivo treatment with nicotine

Effects of prolonged in vivo treatment with nicotine on synaptosomal ATPase activity in rat brain were examined by employing doses of nicotine (0.02 and 0.04 mg/ml in the drinking water) which simulated intake by moderate and heavy smokers. Under these conditions the “low” dose of nicotine resulted in increased body weight whereas “high” dose of nicotine inhibited weight gain. Examination of synaptosomal ATPase activities revealed a dose and time dependent stimulatory/inhibitory effect. With “low” dose of nicotine, maximum stimulatory effect on ATPase activity was seen at the end of the 3rd week, while “high” dose stimulated the enzyme activities maximally by the 2nd week itself; further treatment up to the 4th week caused inhibition of the ATPase activities (10% to 43% decrease).

Dibutyryl-cyclic GMP stimulation of Ca2+ -ATPase activity in rat brain synaptic membranes.

The effects of dibutyryl cyclic AMP (db-cAMP) and dibutyryl cyclic GMP (db-cGMP) were tested on Ca2+-ATPase, Mg2+-ATPase, and (Ca2+ + Mg2+)-ATPase activities in lysed synaptosomes prepared from whole rat brains (minus cerebellum). At concentrations from 0.1 to 2.0 mM, db-cGMP produced a selective, concentration-dependent increase in Ca2+-ATPase activity. Both db-cGMP and db-cAMP slightly reduced Mg2+-ATPase activity, whereas neither compound had concentration-dependent effects on (Ca2+ + Mg2+)-ATPase activity. These findings suggest that the Mg2+-independent, Ca2+-ATPase activity in rat brain is regulated by a cyclic GMP-dependent process. Further, the data provide evidence that the Ca2+-ATPase activity in lysed synaptosomal membranes represents an enzyme that is distinguishable from both the Mg2+ -and (Ca2+ + Mg2+)-ATPase.

Novel microsomal anion-sensitive Mg 2+-ATPase activity in rat brain

Ethacrynic acid (EA) highly sensitive Mg 2+-ATPase activity was demonstrated in rat brain microsomes. Marker enzyme studies suggested that the EA highly sensitive Mg 2+-ATPase activity originated mainly from plasma membranes, and possibly from synaptic vesicles. Oligomycin did not affect the EA highly sensitive Mg 2+-ATPase activity. Sulfhydryl reagents, such as N-ethylmaleimide and 5,5′-dithiobis-(2-nitrobenzoic acid), and anion transport inhibitors, such as 4-acetamide-4′-isothiocyano-stilbene-2,2′-disulfonic acid, 4,4′-diisothiocyano-stilbene-2,2′-disulfonic acid and 2,4-dinitro-1-fluorobenzene, completely inhibited the EA highly sensitive Mg 2+-ATPase activity with apparent K i values at 5, 5, 8, 8 and 10 μM respectively. Treatment of microsomes with ethylenediaminetetraacetic acid and ammonium sulfate increased the EA highly sensitive Mg 2+ and Na +,K +-ATPase activities, but not EA less sensitive Mg 2+- or HCO 3-ATPase activity, 2- to 3-fold that in crude microsomes. Relative substrate specificities of ATP ⪢ GTP > ITP > UTP, CTP, a K m for ATP at 0.77 mM, and an optimal pH at pH 7.4 were observed. Among the anions tested (Cl −, Br −, F −, HCO 3 −, I −, SCN −, NO 3 −), EA highly sensitive Mg 2+-ATPase activity was stimulated significantly by Cl − and reduced by NO 3 −. These data suggest that a novel, plasma membrane-located and anion-sensitive Mg 2+-ATPase activity exists in the brain.

Kinetics of the mechanism of action of monoamine oxidase in the regulation of Na+,K+-ATPase activity in rat brain.

Kinetic studies on the action of monoamine oxidase (MAO) in the regulation of Na+,K+-ATPase were performed using 3-methoxy-4-hydroxybenzaldehyde (MHB), which is an analogue of 3-methoxy-4-hydroxy-phenylacetylaldehyde (product of MAO-catalysed reaction with dopamine as substrate). It was observed that at 2.6 microM MHB, the activation of Na+,K+-ATPase may be the result of the removal of the inhibitory Ca2+, thereby increasing the Vmax. Double-reciprocal plots of Pi versus MHB showed that Ca2+ counteracted the effect of the aldehyde not by changing the Km, but be decreasing the Vmax of the Na+,K+-ATPase stimulation. The removal of 3',5'-cyclic AMP-dependent protein kinase from the microsomes by sodium dodecyl sulphate treatment abolished the activation and/or inhibition of the Na+,K+-ATPase by aldehyde; it can therefore be inferred that 3',5'-cyclic AMP-dependent protein kinase is involved in the regulation of Na+,K+-ATPase.

Inhibition of calcium ATPase activity in rat brain and muscle by chlordecone.

Inhibition of calcium ATPase activity in rat brain and muscle by chlordecone.