Na+,K+-ATPase and Mg2+-ATPase activities in different regions of rat brain during alloxan diabetes

Trigonella foenum-graecum seeds extract plays a beneficial role on brain antioxidant and oxidative status in alloxan-induced Wistar rats

Context

Trigonella foenum-graecum (TriFG) exhibits increased scavenger enzymatic activities and reduces the production of reactive oxygen species in diabetic rats.

Objective

The present study was aimed to investigate the effect of TriFG on lipid peroxidation levels and antioxidant status in brain tissue of rats exposed to alloxan.

Materials and Methods

Healthy male rats (180 ± 10 g) were allocated into five groups. Animals in group 1 maintained on normal tap water served as controls and rats in groups 2, 3, 4, and 5 were treated as experimental groups. Rats in group 2 were intraperitoneally injected with alloxan (120 mg/kg BW) and treated as diabetic rats, whereas rats in groups 3 and 4 were maintained on same experimental regimen as that of rats in groups 1 and 2, respectively, and in addition, they were orally gavaged with herbal extracts of TriFG (0.25 g/kg BW). Diabetic rats treated with glibenclamide in group 5 were used as positive controls.

Results and Discussion

Significant (P < 0.001) increase in the antioxidant enzymes with a significant (P < 0.001) decrease in the lipid peroxidation levels were observed in the brain tissue of diabetic rats treated with TriFG extract as compared to diabetic and glibenclamide-treated rats. No significant changes were observed in pro- and antioxidant levels in brain tissue of rats treated with TriFG extract alone when compared to normal rats. In diabetic rats, brain mitochondrial and cytosolic enzymes like succinate dehydrogenase, glutamate dehydrogenase, and glucose-6-phosphate dehydrogenase activity levels were significantly (P < 0.05) decreased with reversely increased was observed in lactate dehydrogenase activity (P < 0.05).

Conclusions

The findings of the present study suggested that TriFG, through its antioxidant properties, protects brain tissue by mitigating oxidative stress induced by alloxan-exposed rats. TriFG extract significantly increased the antioxidant and oxidative properties in diabetic rats when compared with the control group rats.

Sodium Orthovanadate and Trigonella Foenum Graecum Prevents Neuronal Parameters Decline and Impaired Glucose Homeostasis in Alloxan Diabetic Rats

Hyperglycemia is the most important contributor in the onset and progress of diabetic complications mainly by producing oxidative stress. The present study was carried out to observe, the antihyperglycemic effect of sodium orthovanadate (SOV) and Trigonella foenum graecum seed powder (TSP) administration on blood glucose and insulin levels, membrane linked enzymes (monoamine oxidase, acetylcholinesterase, Ca2+ATPase), intracellular calcium (Ca2+) levels, lipid peroxidation, membrane fluidity and neurolipofuscin accumulation in brain of the alloxan induced diabetic rats and to see whether the treatment with SOV and TSP was capable of reversing the diabetic effects. Diabetes was induced by administration of alloxan monohydrate (15 mg/100 g body weight) and rats were treated with 2 IU insulin, 0.6 mg/ml SOV, 5% TSP in the diet and a combination of 0.2 mg/ml SOV and 5% TSP separately for three weeks. Diabetic rats showed hyperglycemia with almost four fold high blood glucose levels. Activities of acetylcholinesterase and Ca2+ATPase decreased in diabetic rat brain. Diabetic rats exhibited an increased level of intracellular Ca2+ levels, lipid peroxidation, neurolipofuscin accumulations and monoamine oxidase activity. Treatment of diabetic rats with insulin, TSP, SOV and a combined therapy of lower dose of SOV with TSP revived normoglycemia and restored the altered level of membrane bound enzymes, lipid peroxidation and neurolipofuscin accumulation. Our results showed that lower doses of SOV (0.2 mg/ml) could be used in combination with TSP in normalization of altered metabolic parameters and membrane linked enzymes without any harmful side effect.

Antidiabetic and neuroprotective effects of Trigonella foenum-graecum seed powder in diabetic rat brain

Trigonella foenum-graecum seed powder (TSP) has been reported to have hypoglycemic and hyperinsulinemic action. The objective of the study was to examine the antidiabetic and neuroprotective role of TSP in hyperglycemiainduced alterations in blood glucose, insulin levels and activities of membrane linked enzymes (Na+K+ATPase, Ca2+ATPase), antioxidant enzymes (superoxide dismutase, glutathione S-transferase), calcium (Ca2+) levels, lipid peroxidation, membrane fluidity and neurolipofuscin accumulation in the diabetic rat brain. Female Wistar rats weighing between 180 and 220 g were made diabetic by a single injection of alloxan monohydrate (15 mg/100 g body weight), diabetic rats were given 2 IU insulin, per day with 5% TSP in the diet for three weeks. A significant increase in lipid peroxidation was observed in diabetic brain. The increased lipid peroxidation following chronic hyperglycemia was accompanied with a significant increase in the neurolipofuscin deposition and Ca2+ levels with decreased activities of membrane linked ATPases and antioxidant enzymes in diabetic brain. A decrease in synaptosomal membrane fluidity may influence the activity of membrane linked enzymes in diabetes. The present study showed that TSP treatment can reverse the hyperglycemia induced changes to normal levels in diabetic rat brain. TSP administration amended effect of hyperglycemia on alterations in lipid peroxidation, restoring membrane fluidity, activities of membrane bound and antioxidant enzymes, thereby ameliorating the diabetic complications.

Estradiol modulates membrane-linked ATPases, antioxidant enzymes, membrane fluidity, lipid peroxidation, and lipofuscin in aged rat liver

Free radical production and oxidative stress are known to increase in liver during aging, and may contribute to the oxidative damage. These changes increase during menopausal condition in females when the level of estradiol is decreased. The objective of this study was to observe the changes in activities of membrane linked ATPases (Na⁺K⁺ ATPase, Ca²⁺ ATPase), antioxidant enzymes (superoxide dismutase, glutathione-S-transferase), lipid peroxidation levels, lipofuscin content and membrane fluidity occurring in livers of female rats of 3, 12 and 24 months age groups, and to see whether these changes are restored to 3 months control levels rats after exogenous administration of 17-β-estradiol (E2). The aged rats (12 and 24 months) were given subcutaneous injection of E2 (0.1 μg/g body weight) daily for one month. The results obtained in the present work revealed that normal aging was associated with significant decrease in the activities of membrane linked ATPases, antioxidant enzymes, membrane fluidity and an increase in lipid peroxidation and lipofuscin content in livers of aging female rats. The present study showed that E2 treatment reversed the changes to normal levels. E2 treatment may be beneficial in preventing some of the age related changes in the liver by increasing antioxidant defenses.

Protective effects of 17β estradiol on altered age related neuronal parameters in female rat brain

Biological aging is a fundamental process observed in almost all living beings. During aging the brain experiences structural, molecular, and functional alterations. Aging in females and males is considered as the end of natural protection against age related diseases like osteoporosis, coronary heart disease, diabetes, Alzheimer's and Parkinson's disease. These changes increase during menopausal condition in females when the level of estradiol is decreased. The aim of the present study was to investigate the anti-aging and protective potential of 17β estradiol (E2) treatment on activities of membrane linked ATPases (Na⁺K⁺ ATPase, Ca²⁺ATPase), antioxidant enzymes (superoxide dismutases, glutathione-S-transferases), intrasynaptosomal calcium levels, membrane fluidity and neurolipofuscin in the brain of aging female rats of 3 months (young), 12 months (adult) and 24 months (old) age groups, and to see whether these changes are restored to normal levels after exogenous administration of E2 (0.1 μg/g body weight for one month).The results obtained in the present work revealed that normal aging was associated with significant decrease in the activities of membrane linked ATPases, antioxidant enzymes and an increase in neurolipofuscin, intrasynaptosomal calcium levels in brain of aging female rats. The present study showed that E2 treatment reversed the changes to near normal levels. E2 treatment appears to be beneficial in preventing some of the age related changes in the brain, an important anti-aging effect of the hormone.

Effects of adult-onset streptozotocin-induced diabetes on the rat brain antioxidant status and the activities of acetylcholinesterase, (Na(+),K (+))- and Mg(2+)-ATPase: modulation by L-cysteine

Uncontrolled diabetes is known to affect the nervous system. The aim of this study was to investigate the effect of the antioxidant L: -cysteine (Cys) on the changes caused by adult-onset streptozotocin (STZ)-induced diabetes on the rat brain total antioxidant status (TAS) and the activities of acetylcholinesterase (AChE), (Na(+),K(+))-ATPase and Mg(2+)-ATPase. Thirty-eight male Wistar rats were divided into six groups: C(A) (8-week-control), C(B) (8-week-control + 1-week-saline-treated), C + Cys (8-week-control + 1-week-Cys-treated), D(A) (8-week-diabetic), D(B) (8-week-diabetic + 1-week-saline-treated) and D + Cys (8-week-diabetic + 1-week-Cys-treated). All diabetic rats were once treated with an intraperitoneal (i.p.) STZ injection (50 mg/kg body weight) at the beginning of the experiment, while all Cys-treated groups received i.p. injections of Cys 7 mg/kg body weight (daily, for 1-week, during the 9th-week). Whole rat brain parameters were measured spectrophotometrically. In vitro incubation with 0.83 mM of Cys or 10 mM of STZ for 3 h was performed on brain homogenate samples from groups C(B) and D(B), in order to study the enzymes' activities. Diabetic rats exhibited a statistically significant reduction in brain TAS (-28%, D(A) vs C(A);-30%, D(B) vs C(B)) that was reversed after 1-week-Cys-administration into basal levels. Diabetes caused a significant increase in AChE activity (+27%, D(A) vs C(A); +15%, D(B) vs C(B)), that was further enhanced by Cys-administration (+57%, D + Cys vs C(B)). The C + Cys group exhibited no significant difference compared to the C(B) group in TAS (+2%), but showed a significantly increased AChE activity (+66%, C + Cys vs C(B)). Diabetic rats exhibited a significant reduction in the activity of Na(+),K(+)-ATPase (-36%, D(A) vs C(A);-48%, D(B) vs C(B)) that was not reversed after 1-week Cys administration. However, in vitro incubation with Cys partially reversed the diabetes-induced Na(+),K(+)-ATPase inhibition. Mg(2+)-ATPase activity was not affected by STZ-induced diabetes, while Cys caused a significant inhibition of the enzyme, both in vivo (-14%, C + Cys vs C(B);-17%, D + Cys vs C(B)) and in vitro (-16%, D(B) + in vitro Cys vs C(B)). In vitro incubation with STZ had no effect on the studied enzymes. The present data revealed a protective role for Cys towards the oxidative effect of diabetes on the adult rat brain. Moreover, an increase in whole brain AChE activity due to diabetes was recorded (not repeatedly established in the literature, since contradictory findings exist), that was further increased by Cys. The inhibition of Na(+),K(+)-ATPase reflects a possible mechanism through which untreated diabetes could affect neuronal excitability, metabolic energy production and certain systems of neurotransmission. As concerns the use of Cys as a neuroprotective agent against diabetes, our in vitro findings could be indicative of a possible protective role of Cys under different in vivo experimental conditions.

Neuroprotective Role of Neurokinin B (NKB) on β-amyloid (25–35) Induced Toxicity in Aging Rat Brain Synaptosomes: Involvement in Oxidative Stress and Excitotoxicity

The brain tissue has a large oxidative capacity, but its ability to combat oxidative stress is limited. In aging brain tissue the oxidative stress increases due to decreased activity of antioxidant enzymes and increased oxidative stress leading to neurodegeneration associated with excitotoxicity. The aim of the present study was to determine the effect of neuropeptides, neurokinin B (NKB) and amyloid beta protein fragment Abeta (25-35) and neurotransmitters N-methyl D-aspartate (NMDA) and Glutamate on rat brain synaptosomes of different age groups. Aging brain functions were assessed by measuring the activities of superoxide dismutase (Mn-SOD) and monoamine oxidase (MAO) and intrasynaptosomal [Ca(2+)](i )levels in presence of neuropeptides and neurotransmitters. Increase in age decreased the SOD and MAO enzyme activities; Abeta (25-35) addition further had damaging/toxic effects on the enzymes, whereas NKB alone and in combination with amyloid lowered the toxic effects caused by Abeta (25-35) addition, which was concentration (peptide) and age dependent. Oxidative stress and excitotoxicity are major consequences associated with the age, [Ca(2+)](i )was increased with the age and the neuropeptides and neurotransmitters elicited significant modulatory effects on it. Our study elucidates an increased activity of SOD, decreased activity of MAO and restoration of [Ca(2+)](i) levels in the presence of NKB and suggests an antioxidant, neuromodulatory and neuroprotective role of tachykinin peptide NKB against the beta amyloid induced toxicity.

Membrane Associated Functions of Neurokinin B (NKB) on Aβ (25–35) Induced Toxicity in Aging Rat Brain Synaptosomes

The effect of different concentrations (0.1-5 microM) of neurokinin B (NKB) and Abeta (25-35) on acetylcholine esterase (AChE), Na(+)-K(+) ATPase and membrane fluidity (DPH anisotropy) were investigated in rat brain synaptosomes of 3, 9, 18 and 30 months old. An age dependent decrease was observed for all the three parameters studied. An in vitro incubation of isolated brain synaptosomes with Abeta (25-35) showed toxic effects on all the parameters studied and the peptide had concentration and age dependent effects, while NKB showed stimulating effect on the parameters and the combined NKB+Abeta (25-35) incubations showed a partial reversal effect as compared to the Abeta (25-35) alone. Thus, the results suggest a membrane mediated function for NKB and its role in neuromodulation, neuroprotection and antioxidant property against Abeta (25-35) induced toxicity in aging brain functions.

Amelioration of altered antioxidant status and membrane linked functions by vanadium andTrigonella in alloxan diabetic rat brains

Trigonella foenum graecum seed powder (TSP) and sodium orthovanadate (SOV) have been reported to have antidiabetic effects. However, SOV exerts hypoglycemic effects at relatively high doses with several toxic effects. We used low doses of vanadate in combination with TSP and evaluated their antidiabetic effects on anti-oxidant enzymes and membrane-linked functions in diabetic rat brains. In rats, diabetes was induced by alloxan monohydrate (15 mg/100 g body wt.) and they were treated with 2 IU insulin, 0.6 mg/ml SOV, 5% TSP and a combination of 0.2 mg/ml SOV with 5% TSP for 21 days. Blood glucose levels, activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), Na+/K+ ATPase, membrane lipid peroxidation and fluidity were determined in different fractions of whole brain after 21 days of treatment. Diabetic rats showed high blood glucose (P less than 0.001), decreased activities of SOD, catalase and Na+/K+ ATPase (P less than 0.01, P less than 0.001 and P less than 0.01), increased levels of GPx and MDA (P less than 0.01 and P less than 0.001) and decreased membrane fluidity (P less than 0.01). Treatment with different antidiabetic compounds restored the above-altered parameters. Combined dose of Trigonella and vanadate was found to be the most effective treatment in normalizing these alterations. Lower doses of vanadate could be used in combination with TSP to effectively counter diabetic alterations without any toxic effects.

ATPases of synaptic plasma membranes from hippocampus after ischemia and recovery during ageing

Plasticity and relationships between individual ATPases linked to energy-utilizing systems of hippocampus, a very sensitive functional area to both age and ischemia, were studied during ageing on synaptic plasma membranes of 1-year-old "adult" and 2-year-old "aged" rats after 15 min of complete cerebral ischemia and different reperfusion times (01, 24, 48, 72, and 96 h). Activities of Na+, K+, Mg(2+)-ATPase, Mg(2+)-ATPase ouabain insensitive, Na+, K(+)-ATPase, "direct" or "basal" Mg(2+)-ATPase, and acetylcholinesterase (AChE) were evaluated in synaptic plasma membranes, where they play the major role in the regulation of presynaptic nerve ending homeostasis. This in vivo study of recovery time-course from 15 mins of cerebral ischemia indicated specific biochemical assessments of functional meaning: (a) Na+K(+)-ATPase of synaptic plasma membranes in adult and aged animals is stimulated by ischemia; (b) this "hyperactivity" is more markedly related to adult than to aged animals; (c) these abnormalities still persist after 72 and 96 h during the recirculation times, indicating the delayed postischemic suffering of the brain; (d) specific Mg(2+)-ATPase enzyme system possess a lower catalytic power in aged animals than in adult ones, but remained unaltered in adult animals by ischemia and reperfusion; (e) Mg(2+)-ATPase is stimulated in aged animals by ischemia, further increasing during reperfusion up to 72-96 h, indicating the delayed hyperactivity of hippocampus; (f) the increased metabolic activity of hippocampus is indicated by the increased activity of cholinergic system; (g) integrity of synaptic plasma membranes seems not to be altered by 15 min ischemia to a critical extent to compromise their catalytic functionality during reperfusion; (h) AChE activity increases in both adult and aged at some survival times. There are logical reasons for the hypothesis that the modifications in ATPase's catalytic activities in synaptic plasma membranes, which have been modified by ischemia in presynaptic terminals, may play important functional role during recovery time in cerebral tissue in vivo, especially as regards its responsiveness to noxious stimuli, particularly during the recirculation period from acute (or chronic) brain injury.

Oxidative derangement in rat synaptosomes induced by hyperglycaemia: restorative effect of dehydroepiandrosterone treatment

Central nervous system damage in diabetes is caused by both cerebral atherosclerosis and the detrimental effect of chronic hyperglycaemia on nervous tissue. Hyperglycaemia is the primer of a series of cascade reactions causing overproduction of free radicals. There is increasing evidence that these reactive molecules contribute to neuronal tissue damage. Dehydroepiandrosterone (DHEA) has been reported to possess antioxidant properties. This study evaluates the oxidative status in the synaptosomal fraction isolated from the brain of streptozotocin-treated rats and the antioxidant effect of DHEA treatment on diabetic rats. Hydroxyl radical generation, hydrogen peroxide content, and the level of the reactive oxygen species was increased (P<0.05) in synaptosomes isolated from streptozotocin-treated rats. The derangement of the oxidative status was confirmed by a low level of reduced glutathione and alpha-tocopherol. DHEA treatment (4 mg per day for 3 weeks, per os) protected the synaptosomes against oxidative damage: synaptosomes from diabetic DHEA-treated rats showed a significant decrease in reactive species (P<0.05) and in the formation of end products of lipid peroxidation, evaluated in terms of fluorescent chromolipid (P<0.01). Moreover, DHEA treatment restored the unsaturated fatty acid content of the membrane and the reduced glutathione and alpha-tocopherol levels to normal levels and restored membrane NaK-ATPase activity close to control levels. The results demonstrate that DHEA supplementation greatly reduces oxidative damage in synaptosomes isolated from diabetic rats and suggest that this neurosteroid may participate in protecting the integrity of synaptic membranes against hyperglycaemia-induced damage.

Influence of ochratoxin A treatment on the activity of membrane bound enzymes in rat brain regions

Ochratoxin A is a mycotoxin produced by Aspergillus ochraceus and is a natural contaminant of mouldy food. We examined the neuroactive potential of ochratoxin A by measuring the changes in the activities of several membrane bound, cytoplasmic and lysosomal enzymes in the brain of adult female rats, following subchronic application of ochratoxin A. The activities of both soluble and membrane bound fractions of ecto-5'nucleotidase, ecto-Ca2+/Mg2+ATPase, alanine aminopeptidase, gamma-glutamyl transferase, as well as activities of lactate dehydrogenase and of N-acetyl-beta-D-glucosaminidase were followed. Biochemical effects were examined in cerebral cortex, cerebellum and hippocampus. The results obtained showed physiologically significant alterations in the activity of enzymes tested. The changes were found to be time-dependent and regionally selective. Compared to controls, statistically significant increases in gamma-glutamyl transferase were observed in all three brain regions, while in the case of alanine aminopeptidase activities differed with regard to region, the highest increase being observed in hippocampus. Ecto-Ca2+/Mg2+ATPase and ecto-5'nucleotidase showed distinct changes lasting for 20 days of treatment, while increase in the activities of N-acetyl-beta-D-glucosaminidase and lactate dehydrogenase were visible only at the beginning of the treatment. By the end of the trial the activities of almost all enzymes returned back to normal values.

Is the Mg(2+)-ATP-dependent proton pumping activity of the synaptic vesicles a factor involved in the cerebral hypoxia?

The changes in the Mg(2+)-dependent V-type ATPase activity and the Mg(2+)-ATP-dependent H+ pumping activity of the synaptic vesicles from the cerebral cortex of rats submitted to intermittent chronic (4 weeks) mild or severe hypoxia were evaluated. The adaptation to the chronic severe hypoxia increases both the ATPase and the H+ pumping activities which are inhibited by NEM with an exponential relationship between the IC(50) values and the in vivo O2 concentration. The Mg(2+)-dependent increase in H+ pumping activity of synaptic vesicles from the rats subjected to in vivo chronic hypoxia may be antagonized by nigericin (dissipating delta pH) and by FCCP (dissipating delta pH and delta psi SV). In contrast, valinomycin (dissipating the delta psi SV) and facilitating an enhancement in delta pH) increases in vitro the H+ pumping activity that is inhibited by the addition of high concentration of K gluconate (reducing the rate of K+ efflux). The preincubation of vesicles from hypoxic rats with FCCP, but not with nigericin, inhibits the valinomycin-increased H+ pumping activity. L-glutamate increases the H+ pumping activity in synaptic vesicles from the cerebral cortex of chronic hypoxic rats, whereas other amino acids (i.e., L-aspartate and L-homocysteate) and glutamate analogs (i.e., quisqualate and ibotenate) are ineffective. The adaptation to both chronic intermittent severe hypoxia and in vivo treatment with posatireline causes a decrease in the Mg(2+)-ATPase activity consistent with the decrease in the H+ pumping one of the synaptic vesicles. The addition of nigericin into incubation medium magnifies the decrease in the H+ pumping activity, while the addition of FCCP is ineffective, suggesting that the treatment with posatireline interferes with the delta psi SV component in the delta mu H+ of the synaptic vesicles from rats submitted to chronic hypoxia. The results of the in vivo and in vitro experiments suggest that in the synaptic vesicles from hypoxic rats the delta psi SV component in delta mu H+ may be most effective in increasing the Mg(2+)-ATP-dependent H+ pumping activity.

Alterations in the properties and isoform ratios of brain Na+/K(+)-ATPase in streptozotocin diabetic rats

In this study we analysed the changes in the properties of rat cerebral cortex Na+K(+)-ATPase in streptozotocin induced diabetes (STZ-diabetes). Special attempt was made to determine whether insulin treatment of diabetic animals could restore the altered parameters of this enzyme. Na+/K(+)-ATPase activity was found to be decreased by 15% after 2 weeks, and by 37% after 4 weeks in diabetic rat brains with a parallel decrease in maximal capacity of low affinity ouabain binding sites. There was no significant change in the high affinity ouabain binding sites. The Kd values did not change significantly. Western blot analysis of brain Na+/K(+)-ATPase isoforms indicated a 61 +/- 5.8% and 20 +/- 2.8% decrease of the alpha 1 and alpha 3 isoforms, respectively in 4 weeks diabetic animals. Change in the amount of the alpha 2 isoform proved to be less characteristic. Both types of beta subunit isoform showed a significant decrease in four weeks diabetic rats. Our data indicate a good correlation in diabetic rats between changes in Na-/K(+)-ATPase activity, low affinity ouabain binding capacity and the level of alpha 1 isoform. While insulin treatment of diabetic animals restored the blood glucose level to normal, a complete reversal of diabetes induced changes in Na+/K(+)-ATPase activity, ouabain binding capacity and Na+/K(+)-ATPase isoform composition could not be achieved.

Age-related changes by hypoxia and TRH analogue on synaptic ATPase activities

Some synaptosomal energy-requiring ATPases were evaluated in the cerebral cortex from 3- and 24-month-old normoxic rats and rats submitted to either mild or severe chronic (4 weeks) intermittent normobaric hypoxia. Furthermore, 4-week treatment with saline or TRH analogue posatireline was performed. The activities of Na+,K(+)-ATPase, low- and high-affinity Ca(2+)-ATPase, and Ca2+,Mg(2+)-ATPase were assayed in synaptosomes and synaptosomal subfractions, namely synaptosomal plasma membranes and synaptic vesicles. With the exception of the high-affinity Ca(2+)-ATPase, aging induced a decrease in the ATPase activities from normoxic rats. The adaptation to chronic intermittent mild hypoxia was characterized by an increase in the activity of Mg(2+)-ATPase in 3-month-old rats, concomitant with a decrease in the activities of: a) Na+,K(+)-ATPase and high-affinity Ca(2+)-ATPase in both 3- and 24-month-old rats, and b) Ca2+,Mg(2+)-ATPase in 3-month-old ones. The TRH analogue posatireline increased the high-affinity Ca(2+)-ATPase in both 3- and 24-month-old hypoxic rats, concomitant with an increase in Mg(2+)-ATPase activity in 24-month-old ones. The adaptation to chronic intermittent severe hypoxia was characterized by a decrease in the activities of: a) Na+,K(+)-ATPase, Ca2+,Mg(2+)-ATPase and high-affinity Ca(2+)-ATPase in both 3- and 24-month-old rats, and b) low-affinity Ca(2+)-ATPase only in 24-month-old ones. The effect on Mg(2+)-ATPase activity was characterized by a decrease in the enzymatic form located in the synaptic plasma membranes, concomitant with an increase in the form located in the synaptic vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Synaptosomal non-mitochondrial ATPase activities: age-related alterations by chronic normobaric intermittent hypoxia

In synaptosomes and synaptosomal subfractions (namely, synaptosomal plasma membranes and synaptic vesicles) the age-related alteration in the plasticity of synaptic energy-requiring ATPases (Na+, K(+)-ATPase, low- and high-affinity Ca(2+)-ATPase, Mg(2+)-ATPase and Ca2+, Mg(2+)-ATPase) were assayed in the cerebral cortex from 3- and 24-month-old normoxic rats and rats subjected to either mild or severe chronic (4 weeks) intermittent normobaric hypoxia. With the exception of the high-affinity Ca(2+)-ATPase, aging induced a decrease in the ATPase activities from normoxic rats. The adaptation to mild hypoxia was characterized by an increase in the activity of Mg(2+)-ATPase in 3-month-old rats, concomitant with a decrease in the activities of: (i) Na+,K(+)-ATPase and high-affinity Ca(2+)-ATPase in both 3- and 24-month-old rats; and (ii) Ca2+,Mg(2+)-ATPase in 3-month-old ones. The adaptation to chronic intermittent severe hypoxia was characterized by a decrease in the activities of: (i) Na+,K(+)-ATPase, Ca2+,Mg(2+)-ATPase and high-affinity Ca(2+)-ATPase in both 3- and 24-month-old rats and (ii) low-affinity Ca(2+)-ATPase only in 24-month-old ones. The effect on Mg(2+)-ATPase activity was characterized by a decrease in the activity of the enzymatic form located in the synaptic plasma membranes (involved in ATP hydrolysis to adenosine production), concomitant with an increase in the activity of the form located in the synaptic vesicles (involved in the turnover of transmitters, e.g., glutamate).

Modifications by hypoxia and drug treatment of cerebral ATPase plasticity

The plasticity of synaptosomal non-mitochondrial ATPases was evaluated in cerebral cortex from 3-month-old normoxic rats and rats subjected to either mild or severe intermittent normobaric hypoxia [12 hr daily exposure to N2:O2 (90:10 or 91.5:8.5) for four weeks]. The activities of Na+, K(+)-ATPase, low- and high-affinity Ca(2+)-ATPase, Mg(2+)-ATPase, and Ca2+,Mg(2+)-ATPase were assayed in synaptosomes and synaptosomal subfractions, namely synaptosomal plasma membranes and synaptic vesicles. The evaluations were performed after a 4-week treatment with saline (controls) or alpha-adrenergic agents (delta-yohimbine, clonidine), a vasodilator compound (papaverine), and an oxygen-partial pressure increasing agent (almitrine). These treatments differently changed the adaptation to chronic intermittent hypoxia characterized by a decrease in the activity of Na+,K(+)-ATPase, Ca2+,Mg(2+)-ATPase, and high-affinity Ca(2+)-ATPase, concomitant with a modification in the activity of Mg(2+)-ATPase supported in a different way by the enzymatic forms located into the synaptosomal plasma membranes and synaptic vesicles.

Age-related alterations by chronic intermittent hypoxia on cerebral synaptosomal ATPase activities

The age-related alterations in the plasticity of synaptic energy-requiring ATPases [Na+,K(+)-ATPase, low- and high-affinity Ca(2+)-ATPase, Mg(2+)-ATPase, and Ca2+,Mg(2+)-ATPase] were assayed in synaptosomes and synaptosomal subfractions [namely, synaptosomal plasma membranes and synaptic vesicles] in the cerebral cortex from 3- and 24-month-old normoxic rats and rats subjected to either mild or severe chronic (four weeks) intermittent normobaric hypoxia. With the exception of the high-affinity Ca(2+)-ATPase, aging induced a decrease in the ATPase activities from normoxic rats. The adaptation to mild hypoxia was characterized by an increase in the activity of Mg(2+)-ATPase in 3-month-old rats, concomitant with a decrease in the activities of: (i) Na+,K(+)-ATPase and high-affinity Ca(2+)-ATPase in both 3- and 24-month-old rats, and (ii) Ca2+,Mg(2+)-ATPase in 3-month-old ones. The adaptation to chronic intermittent severe hypoxia was characterized by a decrease in the activities of: (i) Na+,K(+)-ATPase, Ca2+,Mg(2+)-ATPase and high-affinity Ca(2+)-ATPase in both 3- and 24-month-old rats, and (ii) low-affinity Ca(2+)-ATPase only in 24-month-old ones. The effect on Mg(2+)-ATPase activity was characterized by a decrease in the activity of the enzymatic form located in the synaptic plasma membranes [involved in ATP hydrolysis to adenosine production], concomitant with an increase in the activity of the form located in the synaptic vesicles [involved in the turnover of transmitters, e.g., glutamate].

Synaptosomal non-mitochondrial ATPase activities and drug treatment

Energy-using non-mitochondrial ATPases were assayed in rat cerebral cortex synaptosomes and synaptosomal subfractions, namely synaptosomal plasma membranes and synaptic vesicles. The following enzyme activities were evaluated: Na+, K+ -ATPase; high- and low-affinity Ca2+ -ATPase; basal Mg(2+)-ATPase; Ca2+, Mg(2+)-ATPase. The evaluations were performed after four week-treatment with saline [controls] or alpha-adrenergic agents (delta-yohimbine, clonidine), energy-metabolism interfering compound (theniloxazine), and oxygen-partial pressure increasing agent (almitrine), in order to define the plasticity and the selective changes in individual ATPases. In rat cerebral cortex, the enzyme adaptation to four-week-treatment with delta-yohimbine or clonidine was characterized by increase in both high- and low-affinity Ca2+ -ATPase activities. The action involves the enzyme form located in the synaptic plasma membranes. The enzyme adaptation to the subchronic treatments with theniloxazine or almitrine was characterized by increase in Na+, K(+)-ATPase or Mg(2+)-ATPase activities, respectively. The action involves the enzymatic forms located in the synaptic plasma membranes. Thus, the pharmacodynamic effects of the agents tested should also be related to the changes induced in the activity of some specific synaptosomal non-mitochondrial ATPases.

Effect of intermittent mild hypoxia and drug treatment on synaptosomal nonmitochondrial ATPase activities

Synaptosomal nonmitochondrial ATPases linked to the energy-utilizing systems were evaluated in cerebral cortex from normoxic rats and rats submitted to mild intermittent normobaric hypoxia [12 hr daily exposure to N2:O2 (90:10) mixture for 4 weeks]. The activities of Na+,K(+)-ATPase; high- and low-affinity Ca(2+)-ATPase; basal Mg(2+)-ATPase; and Ca2+, Mg(2+)-ATPase were assayed in synaptosomes and synaptosomal subfractions, namely, synaptosomal plasma membranes and synaptic vesicles. The evaluations were performed either in normoxic rats or in hypoxic rats submitted to 4-week treatment with saline (controls) or a vasodilator agent (papaverine), an energy-metabolism interfering agent (theniloxazine), a calcium blocker (nicardipine), and a lipid-metabolism interfering agent (phosphatidylcholine) in order to define the plasticity and the selective changes in individual ATPases. In synaptosomes from rat cerebral cortex, the enzyme adaptation to the daily mild intermittent hypoxia for 4 weeks was characterized by an increase in the activity of Mg(2+)-ATPase, concomitant with a decrease in the activities of Na+,K(+)-ATPase, high-affinity Ca(2+)-ATPase, and Ca2+, Mg(2+)-ATPase. In hypoxic rats the enzyme adaptation to the 4-week treatment with phosphatidylcholine was characterized by an increase in Ca2+, Mg(2+)-ATPase activity and a decrease in Mg(2+)-ATPase activity. The action involves the enzymatic form located in the synaptic plasma membranes. In hypoxic rats the adaptation to the 4 week treatment with nicardipine was characterized by an increase in high-affinity Ca(2+)-ATPase activity, while the 4-week-treatment with theniloxazine induced an increase in Na+,K(+)-ATPase activity. The actions of both nicardipine and theniloxazine were related to the enzymatic forms located in the synaptic plasma membranes. The effects on the biophase induced by the sequential cycles of hypoxia/normoxia and the treatment with the various agents tested should also be related to the changes induced in the activity of some synaptosomal ATPases.

Inhibitory effect of insulin and cytoplasmic factor(s) on brain (Na(+) + K+) ATPase

(Na+ + K+)ATPase activity in cerebral cortex was modulated by insulin action depending on the Mg2+ concentration. Thus, in homogenates in the presence of 1-3 mM Mg2+, insulin stimulated the enzyme, whereas in the presence of 4-6 mM Mg2+ inhibition was observed. Exposure of synaptosomal membranes to the soluble fraction resulted in inhibition of ATPase activity in a dose-dependent manner. The inhibitory effect of insulin was regulated by a cytoplasmic factor in a dose-dependent manner. Similar variations to those obtained with a crude synaptosomal fraction were obtained by using a partially purified ATPase. These results indicated the importance of soluble factors in the modulation of ATPase by insulin and add more evidence in support for a role of insulin as a neuromodulator.

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.

Lipid peroxidation and glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase, and glucose-6-phosphate dehydrogenase activities in FeCl3-induced epileptogenic foci in the rat brain

This study investigated the relationship between lipid peroxidation, subsequent activation of antioxidative enzymes, and development of iron-induced epilepsy in the rat. Epileptic foci were produced in rat cerebral cortex by intracortical injection of ferric chloride (FeCl3). The epileptic foci were identified by electrocorticography (ECoG). Epileptiform ECoG activity was shown to occur in the contralateral homotopic cerebral cortex as well. We measured levels of lipid peroxides and changes in the activities of the enzymes: superoxide dismutase (SOD), glutathione peroxidase (GP), glutathione reductase (GR), catalase (CA), and glucose-6-phosphate dehydrogenase (G6P) in the epileptogenic focus (both ipsilateral and contralateral) at days 3, 8, 15, and 23 after FeCl3 injection. Biochemical estimations were made in subcellular fractions, and changes in the ipsilateral site were compared with those in the contralateral site. The results of this study showed that large increases in lipid peroxidation were associated with development and buildup of the ECoG epileptiform discharges. Lipid peroxides increased in the ipsilateral focus by approximately 100% as compared with control. In the contralateral site, however, the increase in lipid peroxides was marginal only. The increase in lipid peroxidation was concomitant with development of the high level of epileptiform activity. The time course of changes in lipid peroxidation paralleled the time course of development and persistence of the epileptiform activity. Regarding changes in the enzyme activities accompanying development of iron epilepsy, the data showed that although SOD and G6P increased by approximately 60% and GR increased by approximately 40%, the increases in the enzyme GP and CA were much lower, less than 20%. Thus, comparatively less increase in CA and GP activities produces a deficiency of these two enzymes in the iron (ipsilateral) focus. Among the various biochemical disturbances that have been identified as involved in epileptogenesis, peroxidative injury resulting from lipid peroxidation in neural plasma membrane may be causally related to development of paroxysmal epileptiform activity in the iron focus. Since GP is an enzyme of major importance in detoxification of lipid peroxides in the brain, based on the results presented in this article, it appears reasonable to suggest that GP deficiency causes lipid peroxidation to increase tremendously during iron epileptogenesis.

M-signal hypothesis--metabolic modulation of membrane functions in rat brain

1. Monoamine oxidase (amine: oxygen oxidoreductase [deaminating], EC 1.4.3.4) (MAO) and Na+/K+ ATPase (Na+/K+-ATPase, Mg2+-dependent ATP phosphohydrolase, EC 3,1,6,3) showed reciprocal relationship in their activity patterns during experimentally perturbed situations in vivo as well as in vitro. 2. M-signal hypothesis is proposed, which attempts at explaining the regulation of plasma membrane function by the intermediate of metabolic processes in the cell. This metabolic intermediate referred to as M-signal exercise its influence on the plasma membrane Na+/K+ ATPase which is responsible for the uptake process.

Cation permeability of the blood-brain barrier in streptozotocin-diabetic rats

Decreased sodium permeability across the blood-brain barrier occurs in streptozotocin-treated rats after 2 weeks of diabetes. To establish whether this is a phenomenon specific for cations, the blood-brain barrier permeability for sodium, potassium and calcium was studied with an arterial integral uptake technique. Experiments were performed in control rats and, after two weeks after diabetes induction, in untreated streptozotocin-diabetic rats and in insulin-treated streptozotocin rats. In untreated diabetes, the neocortical blood-brain barrier permeability for sodium decreased by 35% (5.2 +/- 1.7 vs 3.4 +/- 1.1 10(-5).cm3.s-1.g-1) and potassium permeability by 39% (19.8 +/- 5.7 vs 12.1 +/- 3.9 10(-5).cm3.s-1.g-1), whereas no differences in calcium permeability occurred. Insulin treatment was associated with an increase in the blood-brain barrier permeability to sodium (4.8 +/- 1.0 10(-5).cm3.s-1.g-1) as compared to untreated diabetes (3.4 +/- 1.1 10(-5).cm3.s-1.g-1). It is concluded that the observed changes in sodium and potassium permeability cannot be caused by electrostatic membrane changes. More specific abnormalities of the transport of sodium and potassium across the blood-brain barrier are likely to occur; disturbances in the sodium-potassium-pump activity could account for such alterations.

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.

Effect of 6-aminonicotinamide on monoamine oxidase and Na+K+ATPase activity in different regions of rat brain

The monoamine oxidase activity in the cerebral hemispheres decreased significantly after 2, 4, 8 and 16 hr of 6-amino-nicotinamide (35 mg/kg body weight, i.p.) administration. In the cerebellum, the MAO activity was not affected significantly. In the brain stem, however, a significant increase was observed after 2 hr of drug administration followed by a gradual decrease at later time intervals. The Na+K+ATPase activity in the cerebral hemispheres was increased significantly at 2 and 4 hr of 6-aminonicotinamide administration. This was followed by a gradual decrease at later time intervals. In the cerebellum, like monoamine oxidase, the Na+K+ATPase did not change significantly. The brain stem showed a decrease at 2 hr of drug administration, followed by a significant increase at 4 hr and then a gradual decrease to near control values.

Effects of chlorpromazine on the activities of antioxidant enzymes and lipid peroxidation in the various regions of aging rat brain

In this work, the effect of chronic intraperitoneal administration of chlorpromazine (5 and 10 mg/kg) on the antioxidant enzymes superoxide dismutase (SOD), catalase (CA), glutathione reductase (GR), and glutathione peroxidase (GP); lipid peroxidation; and lipofuscin accumulation in the brains of rats ages 6, 9, and 12 months was studied. Chlorpromazine increased the activities of SOD, GR, and GP in particulate fraction from cerebrum, cerebellum, and brain stem in a dose-dependent manner. While GR and SOD associated with soluble fraction increased, GP associated with soluble fraction was not affected. CA did not change after chlorpromazine administration in any regions of the brain of rats from all age groups. Chlorpromazine, thus, had a somewhat different action on antioxidant enzymes in different subcellular fractions. Chlorpromazine inhibited lipid peroxidation, both in vivo and in vitro, and it also inhibited accumulation of lipid peroxidation fluorescent products (lipofuscin), which was studied histochemically and biochemically as well. The data indicate that chlorpromazine inhibition of lipid peroxidation and of accumulation of lipofuscin can result from elevation of the activity of brain antioxidant enzymes.

Mechanism of the involvement of monoamine oxidase in the regulation of (Na+ + K+)-ATPase in rat brain

Increasing concentrations of dopamine fail to give a biphasic response to (Na+ + K+)-ATPase activity in various subcellular fractions of rat brain preincubated with monoamine oxidase inhibitors, viz. 1 X 10(-4) M clorgyline and 1 X 10(-4) M deprenyl. The product of the monoamine-oxidase-catalysed reaction with dopamine as substrate is 3-methoxy-4-hydroxyphenylacetaldehyde. An analogue of this product is 3-methoxy-4-hydroxybenzaldehyde. This analogue, when incubated with the subcellular fractions which had been preincubated with monoamine oxidase inhibitors and dopamine, gave a more pronounced biphasic response to (Na+ + K+)-ATPase activity than that observed in the fractions incubated with dopamine alone.