RESUMO
In the cropping systems that integrate the corn crop, the insertion of Crotalaria ochroleuca G. Don is predominantly intercropped. In this context, there is a need to observe herbicides that present selectivity for this sunn hemp species. The objective of this study was to evaluate the selectivity of pre and post-emergent herbicides on C. ochroleuca. Two field experiments were conducted in randomized blocks with four replications, involving the pre-emergence and post-emergence application of different herbicide treatments. For the pre-emergent ones, amicarbazone, atrazine and flumioxazin provided phytotoxicity higher than 90% and, consequently, low plant biomass. On the other hand, acetochlor and s-metolachlor did not cause phytotoxicity and did not affect the dry mass of crotalaria. In post-emergence, atrazine + mesotrione showed phytotoxicity >95%, followed by nicosulfuron and 2.4-D with phytotoxicity between 50-60%, whereas tembotrione did not cause injury to the plants. Thus, it was found that among the pre-emergent, acetochlor and s-metolachlor were selective, and for the emerging powders, only tembotrione was the most selective for all parameters analyzed.
Assuntos
Atrazina , Crotalaria , Herbicidas , Herbicidas/toxicidade , Zea maysRESUMO
Ethanol (EtOH) is a drug widely consumed throughout the world that promotes several neurochemical disorders. Its deleterious effects are generally associated with modifications in oxidative stress parameters, signaling transduction pathways, and neurotransmitter systems, leading to distinct behavioral changes. Taurine (2-aminoethanesulfonic acid) is a ß-amino acid not incorporated into proteins found in mM range in the central nervous system (CNS). The actions of taurine as an inhibitory neurotransmitter, neuromodulator, and antioxidant make it attractive for studying a potential protective role against EtOH-mediated neurotoxicity. In this study, we investigated whether acute taurine cotreatment or pretreatment (1 h) prevent EtOH-induced changes in acetylcholinesterase (AChE) activity and in oxidative stress parameters in zebrafish brain. The results showed that EtOH exposure (1% in volume) during 1 h increased AChE activity, whereas the cotreatment with 400 mg·L(-1) taurine prevented this enhancement. A similar protective effect of 150 and 400 mg·L(-1) taurine was also observed when the animals were pretreated with this amino acid. Taurine treatments also prevented the alterations promoted in superoxide dismutase and catalase activities by EtOH, suggesting a modulatory role in enzymatic antioxidant defenses. The pretreatment with 150 and 400 mg·L(-1) taurine significantly increased the sulfydryl levels as compared to control and EtOH groups. Moreover, 150 and 400 mg·L(-1) taurine significantly decreased thiobarbituric acid reactive species (TBARS) levels, but the cotreatment with EtOH plus 400 mg·L(-1) taurine did not prevent the EtOH-induced lipoperoxidation. In contrast, the pretreatment with 150 and 400 mg·L(-1) taurine prevented the TBARS increase besides decreased the basal levels of lipid peroxides. Altogether, our data showed for the first time that EtOH induced oxidative stress in adult zebrafish brain and reinforce the idea that this vertebrate is an attractive alternative model to evaluate the beneficial effect of taurine against acute EtOH exposure.
Assuntos
Acetilcolinesterase/efeitos dos fármacos , Transtornos do Sistema Nervoso Induzidos por Álcool/tratamento farmacológico , Encéfalo/efeitos dos fármacos , Inibidores da Colinesterase/farmacologia , Fármacos Neuroprotetores/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Taurina/farmacologia , Acetilcolinesterase/metabolismo , Transtornos do Sistema Nervoso Induzidos por Álcool/enzimologia , Transtornos do Sistema Nervoso Induzidos por Álcool/metabolismo , Animais , Encéfalo/enzimologia , Encéfalo/metabolismo , Inibidores da Colinesterase/metabolismo , Modelos Animais de Doenças , Feminino , Masculino , Fármacos Neuroprotetores/metabolismo , Estresse Oxidativo/fisiologia , Especificidade da Espécie , Taurina/metabolismo , Peixe-ZebraRESUMO
In the present report the enzymatic properties of an ATP diphosphohydrolase (apyrase, EC 3.6.1.5) in Trichomonas vaginalis were determined. The enzyme hydrolyses purine and pyrimidine nucleoside 5'-di- and 5'-triphosphates in an optimum pH range of 6.0--8.0. It is Ca(2+)-dependent and is insensitive to classical ATPase inhibitors, such as ouabain (1 mM), N-ethylmaleimide (0.1 mM), orthovanadate (0.1 mM) and sodium azide (5 mM). A significant inhibition of ADP hydrolysis (37%) was observed in the presence of 20 mM sodium azide, an inhibitor of ATP diphosphohydrolase. Levamisole, a specific inhibitor of alkaline phosphatase, and P(1), P(5)-di (adenosine 5'-) pentaphosphate, a specific inhibitor of adenylate kinase, did not inhibit the enzyme activity. The enzyme has apparent K(m) (Michaelis Constant) values of 49.2+/-2.8 and 49.9+/-10.4 microM and V(max) (maximum velocity) values of 49.4+/-7.1 and 48.3+/-6.9 nmol of inorganic phosphate x min(-1) x mg of protein(-1) for ATP and ADP, respectively. The parallel behaviour of ATPase and ADPase activities and the competition plot suggest that ATP and ADP hydrolysis occur at the same active site. The presence of an ATP diphosphohydrolase activity in T. vaginalis may be important for the modulation of nucleotide concentration in the extracellular space, protecting the parasite from the cytolytic effects of the nucleotides, mainly ATP.
Assuntos
Apirase/metabolismo , Trichomonas vaginalis/enzimologia , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Cloreto de Cálcio/metabolismo , Inibidores Enzimáticos/farmacologia , Cloreto de Magnésio/metabolismo , Especificidade por SubstratoRESUMO
The effects of transient forebrain ischemia, reperfusion and ischemic preconditioning on rat blood platelet ATP diphosphohydrolase and 5'-nucleotidase activities were evaluated. Adult Wistar rats were submitted to 2 or 10 min of single ischemic episodes, or to 10 min of ischemia 1 day after a 2-min ischemic episode (ischemic preconditioning) by the four-vessel occlusion method. Rats submitted to single ischemic insults were reperfused for 60 min and for 1, 2, 5, 10 and 30 days after ischemia; preconditioned rats were reperfused for 60 min 1 and 2 days after the long ischemic episode. Brain ischemia (2 or 10 min) inhibited ATP and ADP hydrolysis by platelet ATP diphosphohydrolase. On the other hand, AMP hydrolysis by 5'-nucleotidase was increased after 2, but not 10, min of ischemia. Ischemic preconditioning followed by 10 min of ischemia caused activation of both enzymes. Variable periods of reperfusion distinctly affected each experimental group. Enzyme activities returned to control levels in the 2-min group. However, the decrease in ATP diphosphohydrolase activity was maintained up to 30 days of reperfusion after 10-min ischemia. 5'-Nucleotidase activity was decreased 60 min and 1 day following 10-min ischemia; interestingly, enzymatic activity was increased after 2 and 5 days of reperfusion, and returned to control levels after 10 days. Ischemic preconditioning cancelled the effects of 10-min ischemia on the enzymatic activities. These results indicate that brain ischemia and ischemic preconditioning induce peripheral effects on ecto-enzymes from rat platelets involved in nucleotide metabolism. Thus, ATP, ADP and AMP degradation and probably the generation of adenosine in the circulation may be altered, leading to regulation of microthrombus formation since ADP aggregates platelets and adenosine is an inhibitor of platelet aggregation
Assuntos
Animais , Ratos , Masculino , 5'-Nucleotidase/metabolismo , Apirase/metabolismo , Plaquetas/química , Isquemia Encefálica/enzimologia , Análise de Variância , Precondicionamento Isquêmico , Ratos Wistar , Fatores de TempoRESUMO
The effects of transient forebrain ischemia, reperfusion and ischemic preconditioning on rat blood platelet ATP diphosphohydrolase and 5'-nucleotidase activities were evaluated. Adult Wistar rats were submitted to 2 or 10 min of single ischemic episodes, or to 10 min of ischemia 1 day after a 2-min ischemic episode (ischemic preconditioning) by the four-vessel occlusion method. Rats submitted to single ischemic insults were reperfused for 60 min and for 1, 2, 5, 10 and 30 days after ischemia; preconditioned rats were reperfused for 60 min 1 and 2 days after the long ischemic episode. Brain ischemia (2 or 10 min) inhibited ATP and ADP hydrolysis by platelet ATP diphosphohydrolase. On the other hand, AMP hydrolysis by 5'-nucleotidase was increased after 2, but not 10, min of ischemia. Ischemic preconditioning followed by 10 min of ischemia caused activation of both enzymes. Variable periods of reperfusion distinctly affected each experimental group. Enzyme activities returned to control levels in the 2-min group. However, the decrease in ATP diphosphohydrolase activity was maintained up to 30 days of reperfusion after 10-min ischemia. 5'-Nucleotidase activity was decreased 60 min and 1 day following 10-min ischemia; interestingly, enzymatic activity was increased after 2 and 5 days of reperfusion, and returned to control levels after 10 days. Ischemic preconditioning cancelled the effects of 10-min ischemia on the enzymatic activities. These results indicate that brain ischemia and ischemic preconditioning induce peripheral effects on ecto-enzymes from rat platelets involved in nucleotide metabolism. Thus, ATP, ADP and AMP degradation and probably the generation of adenosine in the circulation may be altered, leading to regulation of microthrombus formation since ADP aggregates platelets and adenosine is an inhibitor of platelet aggregation.
Assuntos
5'-Nucleotidase/metabolismo , Apirase/metabolismo , Plaquetas/química , Isquemia Encefálica/enzimologia , Análise de Variância , Animais , Isquemia Encefálica/sangue , Precondicionamento Isquêmico , Masculino , Ratos , Ratos Wistar , Fatores de TempoRESUMO
This study shows the effect of transient global cerebral ischemia (ISC) on hippocampal acetylcholinesterase (AChE) activity. Naive adult Wistar rats received either a brief (2 min) or a long (10 min) ischemic episode by the four-vessel occlusion method. Pre-conditioned rats received double ischemia: a 10 min episode inflicted 24 h after a 2 min event, a condition known to confer cytoprotection to CA1 pyramidal cells of hippocampus. 2 min of ischemia caused an increase in acetylcholinesterase activity both immediately and 30 min after the episode, however enzyme activity was significantly decreased after 24 h of reperfusion. 10 min of ischemia caused an increase in activity both 60 min and 24 h after ischemia. Conversely, pre-conditioned rats displayed lower activity both immediately and 60 min after ischemia. Our results suggest that: a) neuronal death, that follows 10 min of ischemia, is associated to a late increase in acetylcholinesterase activity; b) pre-conditioning is related to diminished acetylcholinesterase activity. This is in agreement with previous evidence that acetylcholinesterase inhibition and maintenance of acetylcholine levels are beneficial for cell surviving after cerebral ischemia.
Assuntos
Acetilcolinesterase/metabolismo , Isquemia Encefálica/metabolismo , Hipocampo/enzimologia , Acetilcolina/metabolismo , Adaptação Fisiológica , Animais , Sobrevivência Celular , Ratos , Ratos Wistar , Reperfusão , Fatores de TempoRESUMO
1. The effect of several central nervous system active drugs was studied in vitro on ATPase-ADPase activity and acetylcholinesterase (AChE) activity from the cerebral cortex of adult rats. 2. Lithium (1.0-10.0 mM) had no effect on either ATPase-ADPase or acetylcholinesterase activity. 3. Imipramine (0.5-5.0 mM), desipramine (0.5-5.0 mM), amitriptyline (0.1-1.0 mM) and diazepam (0.5-2.0 mM) inhibited ATP and ADP hydrolysis at all concentrations tested. 4. AChE activity was altered by imipramine (1.0-2.0 mM) and by diazepam (0.5-2.0 mM). 5. The possible participation of ATP diphosphohydrolase and AChE in the action of these drugs cannot be ruled out. The probable reduction of ATP, ADP and acetylcholine hydrolysis by the inhibitory effect of these drugs is discussed.
Assuntos
Acetilcolinesterase/metabolismo , Adenosina Trifosfatases/metabolismo , Apirase/metabolismo , Fármacos do Sistema Nervoso Central/farmacologia , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/enzimologia , Acetilcolinesterase/análise , Amitriptilina/farmacologia , Animais , Apirase/análise , Desipramina/farmacologia , Diazepam/farmacologia , Hidrolases/análise , Hidrolases/metabolismo , Imipramina/farmacologia , Técnicas In Vitro , Lítio/farmacologia , Ratos , Sinaptossomos/metabolismoRESUMO
ATP diphosphohydrolases are described as ecto-enzymes in several tissues. In the present study, synaptic plasma membrane (SPM) was exposed to a series of agents used to distinguish between peripheral (hydrophilic), G-PI-anchored and transmembrane-polypeptide-anchored membrane proteins. These procedures included: (a) nondetergent extraction, (b) Triton X-114 phase partitioning, (c) phosphatidylinositol-specific phospholipase C (PI-PLC) extraction and (d) protease incubation. In cases (a), (c) and (d) the SPM was incubated with different agents and the ATPase-ADPase activities and the protein concentration was determined in the original sample, in the pellet and in the supernatant obtained after 100,000 g centrifugation. In procedure (b), the SPM was solubilized in 1% triton X-114 and submitted to phase separation onto a sucrose cushion. The aqueous and detergent rich phases obtained by this treatment were assayed for ATPase-ADPase activities and protein determination. The results obtained suggest an intrinsic behaviour for ATP diphosphohydrolase since none of the nondetergent treatments was efficient in removing the enzyme from SPM. Moreover, ATPase and ADPase activities were recovered predominantly (> 50%) in the detergent-rich phase obtained by Triton X-114 partitioning. The enzyme was not released by PI-PLC or proteases. These results indicate that the enzyme is not a GPI-anchored protein, but is probably deeply anchored on the plasma membrane in agreement with the amino acid sequence of the enzyme recently published.
Assuntos
Apirase/isolamento & purificação , Encéfalo/enzimologia , Proteínas de Membrana/isolamento & purificação , Membranas Sinápticas/enzimologia , Animais , Apirase/metabolismo , Detergentes , Masculino , Proteínas de Membrana/metabolismo , Octoxinol , Fosfatidilinositol Diacilglicerol-Liase , Fosfoinositídeo Fosfolipase C , Polietilenoglicóis , Ratos , Ratos Wistar , Solubilidade , Fosfolipases Tipo C/metabolismoRESUMO
Several lines of evidence indicate that ATP may play an important role in Long-Term Potentiation. In this investigation we evaluated the effect of a memory task (step-down inhibitory avoidance) on the synaptosomal ecto-enzymes (ATP diphosphohydrolase and 5'-nucleotidase) involved in the degradation of ATP to adenosine. After the training session, a decrease in the ATPase (40%) and ADPase (29%) activities of ATP diphosphohydrolase as well as was a decrease in 5'-nucleotidase activity (31%) was observed in hippocampal synaptosomes of rats trained and killed immediately after training. In synaptosomes of rats killed 30 minutes after training, a decrease in ATPase activity (28%) was observed. In the test session, no significant changes were observed in the enzyme activities studied. These results provide new information about the activity of ecto-enzymes involved in nucleotide degradation and their possible participation in mechanisms of acquisition and modulation of memory processing.
Assuntos
5'-Nucleotidase/metabolismo , Apirase/metabolismo , Aprendizagem da Esquiva , Hipocampo/enzimologia , Sinaptossomos/enzimologia , Animais , Masculino , Memória , Ratos , Ratos WistarRESUMO
Adenosine, an endogenous neuroprotective agent, can be produced in the synaptic cleft from adenosine triphosphate (ATP) hydrolysis via the concerted action of two enzymes: ATP diphosphohydrolase and 5'-nucleotidase. The aim of the present study was to investigate such enzymatic activities in the hippocampus of rats subjected to single (2- or 10-minute) or double (2+10 minute, with a 24-hour interval in between, named preconditioned group) ischemic episodes. Ischemia was produced by four-vessel occlusion method. Histological analysis showed no cell death in 2-minute ischemia, and up to 90% of pyramidal CA(1) cell loss in the 10-minute ischemic group. As predicted, double ischemic rats displayed a significant cytoprotective effect (around 60%). Preconditioned rats presented a delayed enhancement in ATP diphosphohydrolase activity (for ATP and adenosine diphosphate hydrolysis) after 48 hours of reperfusion. 5'-nucleotidase activity was increased immediately after ischemic insult (for all groups) and after a late reperfusion period (48 hours). We suggest that preconditioning causes delayed changes in enzymatic activities that would conceivably lead to increased adenosine production. This effect could be related to cytoprotection seen in preconditioned rats.
RESUMO
1. 9-Amino-1,2,3,4-tetrahydroacridine (THA), an acetylcholinesterase inhibitor, significantly inhibited in vitro the ATP diphosphohydrolase activity of synaptosomes from the cerebral cortex and hippocampus of adult rats. 2. THA did not inhibit in vitro the 5'-nucleotidase activity of synaptosomes from cerebral cortex and hippocampus of rats. 3. THA exerted an uncompetitive inhibition on ATP diphosphohydrolase activity. This mechanism of inhibition was the same in the 2 different synaptosomal fractions (cerebral cortex and hippocampus) studied. 4. THA, proposed as a drug for the treatment of Alzheimer's disease, can alter in vitro ATP degradation in synaptosomes from the central nervous system.
Assuntos
5'-Nucleotidase/metabolismo , Apirase/antagonistas & inibidores , Encéfalo/efeitos dos fármacos , Inibidores da Colinesterase/farmacologia , Sinaptossomos/efeitos dos fármacos , Tacrina/farmacologia , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Encéfalo/enzimologia , Encéfalo/ultraestrutura , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/enzimologia , Hipocampo/efeitos dos fármacos , Hipocampo/enzimologia , Hidrólise/efeitos dos fármacos , Cinética , Masculino , Ratos , Ratos Wistar , Sinaptossomos/enzimologiaRESUMO
In the present report we demonstrate the in vitro effects of free radicals on an ecto-ATP diphosphohydrolase activity (apyrase, EC 3.6.1.5) from rat blood platelets. Rat blood platelets were exposed to an oxidant-generating system (H2O2/Fe2+/ascorbate) and the ATP diphosphohydrolase activity was inhibited. The enzyme inhibition was prevented by glutathione (GSH) and cysteine but not by trolox as a vitamin E analogue. The TBARS (thiobarbituric acid reactive substances) assay and the determination of sulphydryl groups indicate that the inhibition of the enzyme activity in resting platelets is not related to lipid peroxidation or to oxidation of sulphydryl residues. These results demonstrate the susceptibility of ATP diphosphohydrolase activity from platelets to free radicals and suggest that amino acid residues which are essential for the enzyme function are probably modified.
Assuntos
Apirase/antagonistas & inibidores , Apirase/sangue , Plaquetas/enzimologia , Radicais Livres/farmacologia , Animais , Plaquetas/efeitos dos fármacos , Cisteína/farmacologia , Glutationa/farmacologia , Técnicas In Vitro , Peroxidação de Lipídeos , Masculino , Estresse Oxidativo , Ratos , Ratos WistarRESUMO
The in vitro effects of membrane lipid peroxidation on ATPase-ADPase activities in synaptic plasma membranes from rat forebrain were investigated. Treatment of synaptic plasma membranes with an oxidant generating system (H(2)0(2)/Fe(2+)/ascorbate) resulted in lipid peroxidation and inhibition of the enzyme activity. Besides, trolox as a water soluble vitamin E analogue totally prevented lipid peroxidation and the inhibition of enzyme activity. These results demonstrate the susceptibility of ATPase-ADPase activities of synaptic plasma membranes to free radicals and suggest that the protective effect against lipid peroxidation by trolox prevents the inhibition of enzyme activity. Thus, inhibition of ATPase-ADPase activities of synaptic plasma membranes in cerebral oxidative stress probably is related to lipid peroxidation in the brain.
Assuntos
Adenosina Trifosfatases/metabolismo , Antioxidantes/farmacologia , Apirase/metabolismo , Peroxidação de Lipídeos , Prosencéfalo/enzimologia , Membranas Sinápticas/enzimologia , Vitamina E/farmacologia , Animais , Ácido Ascórbico/farmacologia , Cromanos/farmacologia , Compostos Ferrosos/farmacologia , Peróxido de Hidrogênio/farmacologia , Cinética , Masculino , Ratos , Ratos WistarRESUMO
Aluminum chloride (AlCl3), a neurotoxic compound, inhibited ATP diphosphohydrolase activity of synaptosomes obtained from cerebral cortex of adult rats. The metal ion significantly inhibited ATPase and ADPase activities of the enzyme at all concentrations tested in vitro (0.01, 0.05, 0.5, 5, and 10 mM) in the presence of 1.5 mM calcium. When tested in the absence of Ca2+, and with increasing amounts of Al3+, enzyme activity remained below basal levels, suggesting that the trivalent cation Al3+ is not a substitute for the divalent cation Ca2+ in ATP-Ca2+ and ADP-Ca2+ complexes. The Al3+ inhibition was competitive with respect to Ca2+. The enzyme inhibition was reversed by the addition of deferoxamine (DFO). NaF significantly inhibited ATP diphosphohydrolase activity, and this inhibition was reversed by the addition of Ca2+ to the medium. Such inhibition was not potentiated by AlF4, which is an inhibitor of cation-transport ATPases.
Assuntos
Compostos de Alumínio/toxicidade , Apirase/metabolismo , Adstringentes/toxicidade , Córtex Cerebral/efeitos dos fármacos , Cloretos/toxicidade , Sinaptossomos/enzimologia , Adenosina Trifosfatases/antagonistas & inibidores , Cloreto de Alumínio , Animais , Apirase/antagonistas & inibidores , Cálcio/metabolismo , Córtex Cerebral/enzimologia , Quelantes/farmacologia , Desferroxamina/farmacologia , Interações Medicamentosas , Sinergismo Farmacológico , Inibidores Enzimáticos/toxicidade , L-Lactato Desidrogenase/metabolismo , Masculino , Proteínas/metabolismo , Ratos , Ratos Wistar , Fluoreto de Sódio/toxicidade , Transmissão Sináptica/efeitos dos fármacos , Sinaptossomos/efeitos dos fármacosRESUMO
The effect of different detergents on the ATPase and ADPase activities from synaptic plasma membrane were investigated. Triton X-100, deoxycholate, CHAPS, Nonidet, N-octylglucoside and C12E8, which is commonly used to solubilize plasma membrane proteins, easily inactivated the ATPase and ADPase activities, while digitonin was not harmful to the enzyme. Treatment of the synaptic plasma membrane from rat brain with 0.5% digitonin solubilizes 80% of the proteins and 50% and 60% of ATPase and ADPase, respectively, with the following characteristics: stimulation by Ca2+ in the millimolar range, insensitivity to ATPase inhibitors (ouabain, olygomicyn, orthovanadate), inhibition with sodium azide and NEM and broad substrate specificity for the hydrolysis of nucleoside di- and triphosphate. To further characterize the enzyme solubilized, polyclonal antibodies specific for ATP diphosphohydrolase from potato tuber were tested. Western blot showed that two electrophoretic bands with a molecular mass close to 60-70 kDa had cross-immunoreactivity with antibodies against potato apyrase. The results presented here demonstrate for the first time the solubilization of ATPase and ADPase activities with characteristics of a true ATP diphosphohydrolase from synaptic plasma membrane from rat brain and with cross-immunoreactivity with antibodies against potato apyrase.
Assuntos
Apirase/análise , Encéfalo/enzimologia , Membranas Sinápticas/enzimologia , Animais , Detergentes/farmacologia , Digitonina/farmacologia , Ativação Enzimática/efeitos dos fármacos , Masculino , Ratos , Ratos Wistar , Frações Subcelulares/enzimologiaRESUMO
ATP diphosphohydrolase (EC 3.6.1.5) catalyzes the hydrolysis of diphospho- and triphosphonucleosides and is activated by divalent cations. The enzyme described in rat blood platelets hydrolyzes Ca(2+)-ATP and Ca(2+)-ADP with a high affinity for these Ca(2+)-nucleotide complexes as substrates. In the present paper, we demonstrate that free ATP or free ADP induces inhibition and kinetic alterations of the enzyme from rat blood platelets. From these results, we draw conclusions about the binding of free nucleotides to the enzyme and their action as inhibitors with respect to calcium-nucleotide complex.
Assuntos
Trifosfato de Adenosina/farmacologia , Apirase/antagonistas & inibidores , Plaquetas/enzimologia , Difosfato de Adenosina/metabolismo , Difosfato de Adenosina/farmacologia , Trifosfato de Adenosina/metabolismo , Animais , Apirase/sangue , Sítios de Ligação , Cálcio/metabolismo , Cátions Bivalentes , Ativação Enzimática , Cinética , Masculino , Ratos , Ratos Wistar , Especificidade por SubstratoRESUMO
ATP diphosphohydrolase (EC 3.6.1.5; apyrase) is an enzyme that can promote ATP and ADP hydrolysis to AMP plus inorganic phosphate and depends on divalent cations such as Ca2+ or Mg2+. In previous papers we described this enzyme in the synaptosomal fraction from the central and peripheral nervous system. The present report examines whether cadmium acetate could affect the in vitro activity of the enzyme in the synaptosomal fraction from the cerebral cortex of adult male Wistar rats. Cadmium (Cd2+), a heavy metal with neurotoxic effects, inhibited the enzyme in a concentration-dependent manner. All concentrations tested (0.05-1.0 mM) significantly inhibited the hydrolysis of both substrates (ATP and ADP), with the exception of 0.05 mM on ATP hydrolysis. The kinetic data indicate a noncompetitive inhibition between the cations Cd2+ and Ca2+.
Assuntos
Acetatos , Apirase/antagonistas & inibidores , Cádmio/farmacologia , Córtex Cerebral/enzimologia , Sinaptossomos/enzimologia , Difosfato de Adenosina/metabolismo , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Apirase/metabolismo , Hidrólise , Cinética , Masculino , Ratos , Ratos Wistar , Especificidade por SubstratoRESUMO
Cerebral ischemia causes cell death of vulnerable neurons in mammalian brain. Wistar adult rats (male and female, weighing 180-280 g) were submitted to 2 min, 10 min, or to 2 and 10 min (separated by a 24-h interval) of transient forebrain ischemia by the four-vessel occlusion method. Animals subjected to the longer ischemic episodes had massive necrosis of pyramidal CA1 cells of the hippocampus, while animals receiving double ischemia (2 + 10 min) showed neuronal tolerance to the ischemic insult. ATP-diphosphohydrolase activity from hippocampal synaptosomes was assayed in these three groups (N = 6 animals/group) under two conditions: no reperfusion and 5-min of reperfusion. The control values for ATPase and ADPase activities were 144.7 +/- 18.8 and 60.6 +/- 5.24 nmol Pi min-1 mg protein-1, respectively. The 10-min group without reperfusion showed an enhancement of approximately 20% for ATPase and ADPase activities. In reperfused rats, only the 2-min group had a 20% increase in both enzymatic activities. We suggest that modulation of ATP-diphosphohydrolase activity might be involved in molecular events that follow both ischemia and reperfusion.
Assuntos
Apirase/metabolismo , Hipocampo/enzimologia , Ataque Isquêmico Transitório/enzimologia , Sinaptossomos/enzimologia , Adenosina Trifosfatases/metabolismo , Animais , Feminino , Masculino , Ratos , Ratos Wistar , Reperfusão , Fatores de TempoRESUMO
Cerebral ischemia causes cell death of vulnerable neurons in mammalian brain. Wistar adult rats (male and female, weighing 180-280 g) were submitted to 2 min, 10 min, or to 2 and 10 min (separated by a 24-h interval) of transient forebrain ischemia by the four-vessel occlusion method. Animals subjected to the longer ischemic episodes had massive necrosis of pyramidal CA1 cells of the hippocampus, while animals receiving double ischemia (2 + 10 min) showed neuronal tolerance to the ischemic insult. ATP-diphosphohydrolase activity from hippocampal synaptosomes was assayed in these three groups (N = 6 animals/group) under two conditions: no reperfusion and 5-min of reperfusion. The control values for ATPase and ADPase activities were 144.7 +/- 18.8 and 60.6 +/- 5.24 nmol Pi min-1 mg protein-1, respectively. The 10-min group without reperfusion showed an enhancement of approximately 20 for ATPase and ADPase activities. In reperfused rats, only the 2-min group had a 20 increase in both enzymatic activities. We suggest that modulation of ATP-diphosphohydrolase activity might be involved in molecular events that follow both ischemia and reperfusion.
Assuntos
Animais , Masculino , Feminino , Ratos , Apirase , Ataque Isquêmico Transitório/enzimologia , Hipocampo , Sinaptossomos , Adenosina Trifosfatases , Ratos Wistar , Reperfusão , Fatores de TempoRESUMO
ATP diphosphohydrolase (EC 3.6.1.5; apyrase) is an enzyme that can promote ATP and ADP hydrolysis to AMP plus inorganic phosphate and depends on divalent cations such as Ca2+ or Mg2+. In previous papers we described this enzyme in the synaptosomal fraction from the central and peripheral nervous system. The present report examines whether cadmium acetate could affect the in vitro activity of the enzyme in the synaptosomal fraction from the cerebral cortex of adult male Wistar rats. Cadmium (Cd2+), a heavy metal with neurotoxic effects, inhibited the enzyme in a concentration-dependent manner. All concentrations tested (0.05-1.0 mM) significantly inhibited the hydrolysis of both substrates (ATP and ADP), with the exception of 0.05 mM on ATP hydrolysis. The kinetic data indicate a noncompetitive inhibition between the cations Cd2+ and Ca2+.